Add 'webapp2' alias for 'google.appengine.ext.webapp'.

Follow up to #1121.

**Main changes:**
* When snippets are generated, snippet metadata is also generated.
* If a method has a snippet, that snippet is included in the method docstring.

**Other changes:**
* Removed the method docstring in the code snippet file (line right below the method definition) since the same text is already in the comment block at the top of the file.
* Removed the concept of a "standalone" sample. All generated samples are expected to be standalone. When someone wants a smaller portion of the sample (e.g., request initialization only) they should fetch it from the file by looking up the line numbers in the snippet metadata file.

Other Notes:
* ~It doesn't look like it's possible to do type annotations with `_pb2` types, so those are annotated as `Any`.~ It is possible to do mypy checking with https://github.com/dropbox/mypy-protobuf, but I think it will be easier make that change in a separate PR.
* There are a lot of golden file updates, [this range of commits](https://github.com/googleapis/gapic-generator-python/pull/1129/files/872c156f5100f1de20631dd59d083206432db374) has _most_ of the generator and test changes.

This PR contains the following updates:

| Package | Change |
[Age](https://docs.renovatebot.com/merge-confidence/) |
[Confidence](https://docs.renovatebot.com/merge-confidence/) |
|---|---|---|---|
| [apache-beam](https://beam.apache.org) | `==2.65.0` -> `==2.69.0` |
![age](https://developer.mend.io/api/mc/badges/age/pypi/apache-beam/2.69.0?slim=true)
|
![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/apache-beam/2.65.0/2.69.0?slim=true)
|
|
[google-cloud-bigtable](https://redirect.github.com/googleapis/python-bigtable)
| `==2.30.1` -> `==2.34.0` |
![age](https://developer.mend.io/api/mc/badges/age/pypi/google-cloud-bigtable/2.34.0?slim=true)
|
![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/google-cloud-bigtable/2.30.1/2.34.0?slim=true)
|
|
[google-cloud-core](https://redirect.github.com/googleapis/python-cloud-core)
| `==2.4.3` -> `==2.5.0` |
![age](https://developer.mend.io/api/mc/badges/age/pypi/google-cloud-core/2.5.0?slim=true)
|
![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/google-cloud-core/2.4.3/2.5.0?slim=true)
|
|
[google-cloud-monitoring](https://redirect.github.com/googleapis/google-cloud-python/tree/main/packages/google-cloud-monitoring)
([source](https://redirect.github.com/googleapis/google-cloud-python)) |
`==2.27.1` -> `==2.28.0` |
![age](https://developer.mend.io/api/mc/badges/age/pypi/google-cloud-monitoring/2.28.0?slim=true)
|
![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/google-cloud-monitoring/2.27.1/2.28.0?slim=true)
|
|
[google-cloud-testutils](https://redirect.github.com/googleapis/python-test-utils)
| `==1.6.4` -> `==1.7.0` |
![age](https://developer.mend.io/api/mc/badges/age/pypi/google-cloud-testutils/1.7.0?slim=true)
|
![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/google-cloud-testutils/1.6.4/1.7.0?slim=true)
|

---

### Release Notes

<details>
<summary>googleapis/python-bigtable (google-cloud-bigtable)</summary>

###
[`v2.34.0`](https://redirect.github.com/googleapis/python-bigtable/blob/HEAD/CHANGELOG.md#2340-2025-10-16)

[Compare
Source](https://redirect.github.com/googleapis/python-bigtable/compare/v2.33.0...v2.34.0)

##### Features

- Add support for Python 3.14
([#&#8203;1217](https://redirect.github.com/googleapis/python-bigtable/issues/1217))
([263332a](https://redirect.github.com/googleapis/python-bigtable/commit/263332af71a229cb4fa598008a708137086a6f67))

###
[`v2.33.0`](https://redirect.github.com/googleapis/python-bigtable/blob/HEAD/CHANGELOG.md#2330-2025-10-06)

[Compare
Source](https://redirect.github.com/googleapis/python-bigtable/compare/v2.32.0...v2.33.0)

##### Features

- Add support for Proto and Enum types
([#&#8203;1202](https://redirect.github.com/googleapis/python-bigtable/issues/1202))
([34ceb86](https://redirect.github.com/googleapis/python-bigtable/commit/34ceb86007db08d453fa25cca4968d5b498ffcd6))
- Expose universe\_domain for tpc
([#&#8203;1150](https://redirect.github.com/googleapis/python-bigtable/issues/1150))
([451fd97](https://redirect.github.com/googleapis/python-bigtable/commit/451fd97e435218ffed47d39423680ffc4feccac4))

##### Bug Fixes

- Fix instance registration cleanup on early iterator termination
([#&#8203;1216](https://redirect.github.com/googleapis/python-bigtable/issues/1216))
([bbfd746](https://redirect.github.com/googleapis/python-bigtable/commit/bbfd746c61a6362efa42c7899ec3e34ceb541c83))
- Refactor channel refresh
([#&#8203;1174](https://redirect.github.com/googleapis/python-bigtable/issues/1174))
([6fa3008](https://redirect.github.com/googleapis/python-bigtable/commit/6fa30084058bc34d4487d1fee5c87d7795ff167a))

###
[`v2.32.0`](https://redirect.github.com/googleapis/python-bigtable/blob/HEAD/CHANGELOG.md#2320-2025-08-01)

[Compare
Source](https://redirect.github.com/googleapis/python-bigtable/compare/v2.31.0...v2.32.0)

##### Features

- Add Idempotency to Cloud Bigtable MutateRowsRequest API
([#&#8203;1143](https://redirect.github.com/googleapis/python-bigtable/issues/1143))
([c3e3eb0](https://redirect.github.com/googleapis/python-bigtable/commit/c3e3eb0e4ce44ece72b150dc5822846627074fba))
- Add support for AddToCell in Data Client
([#&#8203;1147](https://redirect.github.com/googleapis/python-bigtable/issues/1147))
([1a5b4b5](https://redirect.github.com/googleapis/python-bigtable/commit/1a5b4b514cadae5c83d61296314285d3774992c5))
- Implement SQL support in test proxy
([#&#8203;1106](https://redirect.github.com/googleapis/python-bigtable/issues/1106))
([7a91bbf](https://redirect.github.com/googleapis/python-bigtable/commit/7a91bbfb9df23f7e93c40b88648840342af6f16f))
- Modernized Bigtable Admin Client featuring selective GAPIC generation
([#&#8203;1177](https://redirect.github.com/googleapis/python-bigtable/issues/1177))
([58e7d37](https://redirect.github.com/googleapis/python-bigtable/commit/58e7d3782df6b13a42af053263afc575222a6b83))

###
[`v2.31.0`](https://redirect.github.com/googleapis/python-bigtable/blob/HEAD/CHANGELOG.md#2310-2025-05-22)

[Compare
Source](https://redirect.github.com/googleapis/python-bigtable/compare/v2.30.1...v2.31.0)

##### Features

- Add deletion\_protection support for LVs
([#&#8203;1108](https://redirect.github.com/googleapis/python-bigtable/issues/1108))
([c6d384d](https://redirect.github.com/googleapis/python-bigtable/commit/c6d384d4a104c182326e22dc3f10b7b905780dee))
- Support authorized views
([#&#8203;1034](https://redirect.github.com/googleapis/python-bigtable/issues/1034))
([97a0198](https://redirect.github.com/googleapis/python-bigtable/commit/97a019833d82e617769c56761aa5548d3ab896b9))
- Throw better error on invalid metadata response
([#&#8203;1107](https://redirect.github.com/googleapis/python-bigtable/issues/1107))
([2642317](https://redirect.github.com/googleapis/python-bigtable/commit/2642317077b723ca8fd62aa86322b524868c2c4d))

##### Bug Fixes

- Re-add py-typed file for bigtable package
([#&#8203;1085](https://redirect.github.com/googleapis/python-bigtable/issues/1085))
([0c322c7](https://redirect.github.com/googleapis/python-bigtable/commit/0c322c79ecbe4cde3e79d8e83ac655a978d07877))

</details>

<details>
<summary>googleapis/python-cloud-core (google-cloud-core)</summary>

###
[`v2.5.0`](https://redirect.github.com/googleapis/python-cloud-core/blob/HEAD/CHANGELOG.md#250-2025-10-27)

[Compare
Source](https://redirect.github.com/googleapis/python-cloud-core/compare/v2.4.3...v2.5.0)

##### Features

- Add Python 3.14 support
([#&#8203;333](https://redirect.github.com/googleapis/python-cloud-core/issues/333))
([c26e587](https://redirect.github.com/googleapis/python-cloud-core/commit/c26e587a79b1905f4d64e409b853d9e50bbb6c17))

##### Bug Fixes

- Remove setup.cfg configuration for creating universal wheels
([#&#8203;332](https://redirect.github.com/googleapis/python-cloud-core/issues/332))
([78ce8a6](https://redirect.github.com/googleapis/python-cloud-core/commit/78ce8a6f7c781cf2585131d7961beec9069a206c))
- Resolve issue where pre-release versions of dependencies are installed
([#&#8203;329](https://redirect.github.com/googleapis/python-cloud-core/issues/329))
([ab9785d](https://redirect.github.com/googleapis/python-cloud-core/commit/ab9785d1bce1d50a03ff41d9b377dc7632772105))

</details>

<details>
<summary>googleapis/google-cloud-python
(google-cloud-monitoring)</summary>

###
[`v2.28.0`](https://redirect.github.com/googleapis/google-cloud-python/compare/google-cloud-speech-v2.27.0...google-cloud-speech-v2.28.0)

[Compare
Source](https://redirect.github.com/googleapis/google-cloud-python/compare/google-cloud-monitoring-v2.27.2...google-cloud-monitoring-v2.28.0)

###
[`v2.27.2`](https://redirect.github.com/googleapis/google-cloud-python/releases/tag/google-cloud-monitoring-v2.27.2):
google-cloud-monitoring: v2.27.2

[Compare
Source](https://redirect.github.com/googleapis/google-cloud-python/compare/google-cloud-monitoring-v2.27.1...google-cloud-monitoring-v2.27.2)

##### Documentation

- Update import statement example in README
([868b006](https://redirect.github.com/googleapis/google-cloud-python/commit/868b0069baf1a4bf6705986e0b6885419b35cdcc))

</details>

<details>
<summary>googleapis/python-test-utils (google-cloud-testutils)</summary>

###
[`v1.7.0`](https://redirect.github.com/googleapis/python-test-utils/blob/HEAD/CHANGELOG.md#170-2025-10-29)

[Compare
Source](https://redirect.github.com/googleapis/python-test-utils/compare/v1.6.4...v1.7.0)

##### Features

- Add Python 3.14 support
([#&#8203;284](https://redirect.github.com/googleapis/python-test-utils/issues/284))
([3cb8491](https://redirect.github.com/googleapis/python-test-utils/commit/3cb8491d67d65d2262aa1b65091ea9b615b583af))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

👻 **Immortal**: This PR will be recreated if closed unmerged. Get
[config
help](https://redirect.github.com/renovatebot/renovate/discussions) if
that's undesired.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/googleapis/python-bigtable).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MC4xNi4wIiwidXBkYXRlZEluVmVyIjoiNDIuMzIuMiIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>