feat: [Bigtable] Publish AvroSchema to CBT admin API

[gcf-owl-bot]

• Regenerate this pull request now.

docs: Modify ProtoSchema description
docs: Add AvroSchema description

PiperOrigin-RevId: 974526241

Source-Link: googleapis/googleapis@2295794

Source-Link: https://github.com/googleapis/googleapis-gen/commit/4ae7092b73e329ae92be1987404eae19a5b7bf92
Copy-Tag: eyJwIjoiQmlndGFibGUvLk93bEJvdC55YW1sIiwiaCI6IjRhZTcwOTJiNzNlMzI5YWU5MmJlMTk4NzQwNGVhZTE5YTViN2JmOTIifQ==

BEGIN_NESTED_COMMIT
chore: [Bigtable] configure grpc service config for PHP Bigtable
PiperOrigin-RevId: 972068784

Source-Link: googleapis/googleapis@1182557

Source-Link: https://github.com/googleapis/googleapis-gen/commit/44cbd81232e3b93b394628be36ac3520ce6baaee
Copy-Tag: eyJwIjoiQmlndGFibGUvLk93bEJvdC55YW1sIiwiaCI6IjQ0Y2JkODEyMzJlM2I5M2IzOTQ2MjhiZTM2YWMzNTIwY2U2YmFhZWUifQ==
END_NESTED_COMMIT

[JoeWang1127]

The Bigtable conformance test TestMutateRow_Generic_DeadlineExceeded failed after introducing the gRPC service configuration. With the new retry policy, MutateRow now treats DEADLINE_EXCEEDED as retryable.

During the test, a 2-second perOperationTimeout is configured against a mock server with a 10-second sleep. Previously, the test proxy only passed timeoutMillis without specifying retrySettings.totalTimeoutMillis.

When the initial 2-second call timed out with DEADLINE_EXCEEDED, GAX fell back to the default 60-second total timeout and initiated a retry. The Go mock server in cloud-bigtable-clients-test was only configured for a single request, causing a nil pointer dereference panic when the unexpected retry request arrived.

Fix this by setting retrySettings.totalTimeoutMillis in ProxyService::MutateRow, aligning it with other retryable methods (ReadRow, ReadRows, BulkMutateRows) so that GAX respects the total per-operation deadline and ceases retrying once the timeout is reached.

[bshaffer]

Adding "Do Not Merge" label until we hear back from Bigtable that these changes are safe

[snippet-bot]

No region tags are edited in this PR.

This comment is generated by snippet-bot.
If you find problems with this result, please file an issue at:
https://github.com/googleapis/repo-automation-bots/issues.
To update this comment, add snippet-bot:force-run label or use the checkbox below:

• Refresh this comment

[gcf-owl-bot]

Owl bot is regenerating pull request 9601...
Build name: Y2M1NDVjMjgtY2E5Ny00N2JjLWI5YjAtYTY4ZWM1YjBlMGY4

[JoeWang1127]

@bshaffer Can we close this pull request? Librarian manages library updates now.

[bshaffer]

@JoeWang1127 no problem at all... I was just hoping to use it to test my changes for the failing comnformance tests before closing it