Type mysql dialect

Type mysql dialect

Tipyng of mysql dialect.

possible breaking changes:

- on `visit_sequence`, `visit_true` and `visit_false` I changed the param names to be the same tht in the super class.
- Removed  `tostring` on `array`. `tostring` is deprecated since Python 3.2 and removed in Python3.9 so i guess we can remove that option altogheter.
- create_connect_args on aiomysql, added an unused param _translate_args, only to have same signature as super class.
-  delete _check_unicode_returns method. on MySQLDialect_mysqldb. I think is not used after https://gerrit.sqlalchemy.org/c/sqlalchemy/sqlalchemy/+/1946, and is calling to a super that I think doesnt exist anymore.
- delete _set_isolation_level, is unused, and has a super that doesnt exists anymore:
https://github.com/sqlalchemy/sqlalchemy/commit/af1b91626f63e00e11d07ad378d23198abc7f91f
- Separate _bitmap in enumerated to _bitmap and _inversed_bitmap to have type safety
- Add inheritance from log.Identified to MySQLTableDefinitionParser, because has the decorathor @log.class_logger

Related to issue :
https://github.com/sqlalchemy/sqlalchemy/issues/6810

Closes: #12164
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/12164
Pull-request-sha: b877ccab90864cd8d514809e8ad1a6cab7b20494

Change-Id: I37bd98049ff1a64d58e9490b0e5e2ea764dd1f73