[3.10] gh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` (GH-102790)

This is a manual backport of https://github.com/python/cpython/pull/102722 but without `typing.py` changes and without `TypeVarTuple` case, because it was added in 3.11

Automerge-Triggered-By: GH:AlexWaygood