…esults, will revert

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

…esults, will revert part II

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

…transaction_with_batch_update thread-safe\n\nUses a custom assertion to compare call arguments and metadata structure\nwithout relying on the exact order of execution in threads, and more robustly checks the request IDs.

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 833474957

Source-Link:
googleapis/googleapis@7418c8b

Source-Link:
googleapis/googleapis-gen@f969a4a
Copy-Tag:
eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiZjk2OWE0YTVhZDk5N2JhZjE4OWMzOTkzMTYyOTdkNjBhODE5ODg1YiJ9

BEGIN_NESTED_COMMIT
feat: Add Send and Ack mutations for Queues
feat: Add QueryAdvisorResult for query plan
docs: Update description for the BatchCreateSessionsRequest and Session
docs: Update description for the IsolationLevel

PiperOrigin-RevId: 832425466

Source-Link:
googleapis/googleapis@0eeb1be

Source-Link:
googleapis/googleapis-gen@bae4179
Copy-Tag:
eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiYmFlNDE3OTI1MjAzZTY4YzgwNmQ5ZjZiZmUzYzIwYWIzY2JmNWQ4NiJ9
END_NESTED_COMMIT

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Make built-in metrics enabled by default

This change inverts the logic for enabling built-in OpenTelemetry
metrics. Previously, metrics were disabled by default and could be
enabled by setting `ENABLE_SPANNER_METRICS_ENV_VAR=true`.

With this update, metrics are now enabled by default to provide better
out-of-the-box observability for users.

To disable metrics, users must now set the new environment variable:
`SPANNER_DISABLE_BUILTIN_METRICS=true`

The old `ENABLE_SPANNER_METRICS_ENV_VAR` is no longer used. Unit tests
have been updated to reflect this new opt-out behavior.

**BREAKING CHANGE**: Built-in metrics are now enabled by default. Users
who previously did not set any environment variables will have metrics
collection and export turned on automatically after upgrading. To
restore the previous behavior and disable metrics, thry have to set the
`SPANNER_DISABLE_BUILTIN_METRICS` environment variable to `true`.

…concurrent_statement_should_begin_one_transaction_with_read

…ment_should_begin_one_transaction_with_read