Type annotations for sqlalchemy.ext.automap

Type annotations for sqlalchemy.ext.automap

An attempt to annotate `lib/sqlalchemy/ext/automap.py` with type hints (issue [#6810](https://github.com/sqlalchemy/sqlalchemy/issues/6810#issuecomment-1127062951)).

More info on how I approach it could be found in [the earlier PR](https://github.com/sqlalchemy/sqlalchemy/pull/8775).

This pull request is:

- [ ] A documentation / typographical error fix
  - Good to go, no issue or tests are needed
- [ ] A short code fix
  - please include the issue number, and create an issue if none exists, which
    must include a complete example of the issue. one line code fixes without an
    issue and demonstration will not be accepted.
  - Please include: `Fixes: #<issue number>` in the commit message
  - please include tests. one line code fixes without tests will not be accepted.
- [x] A new feature implementation
  - please include the issue number, and create an issue if none exists, which must
    include a complete example of how the feature would look.
  - Please include: `Fixes: #<issue number>` in the commit message
  - please include tests.

**Have a nice day!**

Closes: #8874
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/8874
Pull-request-sha: 834d58d77c2cfd09ea874f01eb7b75a2ea0db7cd

Change-Id: Ie64b2be7a51ddc83ef8f23385fb63db5b5c1bc17