repair mapper sort

repair mapper sort

Fixed issue in :meth:`_orm.Session.bulk_save_mappings` where the sorting
that takes place when the ``preserve_order`` parameter is set to False
would sort partially on ``Mapper`` objects, which is rejected in Python
3.11.

Also uses typing_extensions for NotRequired as this symbol
does not seem to be in Python 3.11.0a4 yet.

For interim 3.11 support, adds the git main build of greenlet
for Python 3.11

Fixes: #7591
Change-Id: I24a62f2322ad7dac5d8e4a00853f8a9408877c9c