feat: add return_last_result annotation to sql

[HugoCasa]

[!IMPORTANT] Add return_last_result annotation to SQL executors to conditionally return only the last result of queries.

• Behavior:
  • Add return_last_result annotation handling in SQL executors (bigquery_executor.rs, mssql_executor.rs, mysql_executor.rs, pg_executor.rs, snowflake_executor.rs).
  • Modify query execution to conditionally skip result collection based on return_last_result.
• Functions:
  • Add get_sql_annotations() in worker.rs to parse SQL annotations.
  • Update do_bigquery_inner(), do_mssql(), do_mysql_inner(), do_postgresql_inner(), do_snowflake_inner() to handle return_last_result.
• Misc:
  • Update SQL script templates in script_helpers.ts to include return_last_result annotation.

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