Run several SQL statements with an explicit transaction

Runs up to 100 statements against the project's schema with the project service key. Each entry is exactly one statement. transaction "all" (default) runs them in one transaction: the first failure rolls back every statement and answers 400 SQL_BATCH_STATEMENT_FAILED naming its index. transaction "each" gives every statement its own transaction and reports each outcome, so later statements still run; status is "partial" when any failed.