Add full support for PEP 695 like syntax

[sydney-runkle]

We currently have a variety of cases that fail (or just don't actually work) with syntax specified in https://peps.python.org/pep-0695/

Let's fix this for v2.11!

[sydney-runkle]

#8984

[changhc]

Hi @sydney-runkle, I would like to work on this issue. I'll start from the cases mentioned in the referenced issue.