text: Title: LAST_INSERT_ID() returns 0 when sharing a cursor.execute(...) call with INSERT
  Body: Windows 10 Home 1903 (18362.720)
  Python 3.8.2 x64, aiomysql 0.0.20
  MariaDB 10.4
  
  Using `Pool` with `auto_commit=True`
  
  Querying `SELECT LAST_INSERT_ID();` within the same `await cursor.execute(...)` call as the `INSERT...;` query the `LAST_INSERT_ID()` should be referencing causes the next `await cursor.fetchone()` call to yield an empty list (this is on a "clean" cursor).
  
  A current workaround involves splitting the `SELECT LAST_INSERT_ID();` and `INSERT...;` queries into separate `await cursor.execute(...)` calls. This yields expected behaviour of `await cursor.fetchone()`. 
  
  I have not tested whether this behaviour is inherited from PyMySQL, rather than aiomysql.
  
  Considering most documentation on SQL best practice indicates it is ideal to keep the `SELECT LAST_INSERT_ID();` close to whatever `AUTO_INCREMENT` it is referencing, requiring two `await cursor.execute(...)` calls may be considered a non-ideal case. Please do let me know if I have configured my environment in a fashion that causes this behaviour.
  
  Many thanks
  fwf