Allow get query as string for dbapi curson execute method

[rekby]

https://github.com/ydb-platform/ydb-sqlalchemy/blob/48cc1c2e53a9c23be6dc371177dda644a6447b00/ydb_sqlalchemy/dbapi/cursor.py#L117

Now it can work with some additional mark for ddl queries and it should work fine after switch the dbapi to ydb query service.