feat(tool/postgres): add postgres-execute-sql-many and postgres-sql-many

[duwenxin99]

Add 2 new tools using the Cloud SQL Admin instances.executeSql API to enable SQL execution against instances provided at runtime:

• postgres-execute-sql-many: Allows execution of arbitrary SQL statements on a specific database provided at runtime.
• postgres-sql-many: Allows execution of prepared SQL statement on a specific instance provided at runtime.

Add prebuilt config for the postgres-execute-sql-many tool to cloud-sql-postgres-admin.

[gemini-code-assist]

Code Review

This pull request introduces the postgres-execute-sql-many and postgres-sql-many tools and adds an ExecuteSql method to the Cloud SQL Admin source. Review feedback identifies several improvement opportunities, including the removal of the unused region parameter in both tools and the cleanup of the postgressqlmany configuration by removing the unsupported Parameters field and its associated runtime checks.

[duwenxin99]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces the postgres-execute-sql-many and postgres-sql-many tools, enabling SQL execution on Cloud SQL Postgres instances provided at runtime. The changes encompass tool implementations, documentation, prebuilt configuration updates, and integration tests. Review feedback suggests appending " Tool" to the documentation titles for both tools to maintain consistency.