fix: preserve optional logger for search support probe

[Will-hxw]

Background

PR #1095 adds debug logging to the Atlas Search capability probe. That changes ConnectionStateConnected.isSearchSupported() from a no-argument public method to requiring a LoggerBase, which can break direct consumers even though the normal Session path passes a logger.

What Changed

• Made the logger parameter optional for ConnectionStateConnected.isSearchSupported().
• Fall back to the existing NullLogger when the method is called directly without a logger.
• Updated the public API reports to show the optional parameter.
• Added a unit test covering direct no-argument calls.

Not Changed

• The search capability probe behavior is unchanged.
• The database candidate order and bounded candidate list from fix: use dynamic database lookup for search index check #1095 are unchanged.
• The integration test harness changes from fix: use dynamic database lookup for search index check #1095 are unchanged.

Risk

Low. Existing internal calls still pass the session logger. Direct calls without a logger keep working and simply use no-op logging during the first probe.

Validation

• pnpm exec vitest --project unit-and-integration tests/unit/common/session.test.ts --run
• pnpm run check:types
• pnpm run check:api
• pnpm run check:format
• pnpm run check:lint
• pnpm run check:dependencies
• pnpm run check

Linked Issues

Supports #1095 / #1022.

[nirinchev]

hey, thanks for that - I was debating with myself whether we should do it as an optional or required - I went for the latter because I figured this is only called internally. Do you have a use case for calling isSearchSupported()?