Add gitutils tests (#71580)
Summary:
Test PeekableIterator behavior
Add `.github/scripts/test_*.py` to list of tests run by test_tools
workflow and pin Python version to 3.7 in test_tools workflow
Change PeekableIterator inheritance from collections.abc.Iterator, to
typing.Iterator, which is a correct alias starting from Python-3.7
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71580
Reviewed By: bigfootjon
Differential Revision: D33690659
Pulled By: malfet
fbshipit-source-id: 71f270b15138230772e2eed0da66cdfcb34825cc
(cherry picked from commit 42abb07396fa90272afb0b56508bd3a1f5c4ccbe)
