Add PEP 646 integration

Add PEP 646 integration

The :class:`.Row` object now no longer makes use of an intermediary
``Tuple`` in order to represent its individual element types; instead,
the individual element types are present directly, via new :pep:`646`
integration, now available in more recent versions of Mypy.  Mypy
1.7 or greater is now required for statements, results and rows
to be correctly typed.   Pull request courtesy Yurii Karabas.

Fixes: #10635
Closes: #10634
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/10634
Pull-request-sha: 430785c8a04a48fe96ce35b4f4e08476700c1f79

Change-Id: Ibd0ae31a98b4ea69dcb89f970e640920b2be6c48