Lazily evaluate all PEP 695 type alias values

[charliermarsh]

Summary

In #7968, I introduced a regression whereby we started to treat imports used only in type annotation bounds (with __future__ annotations) as unused.

The root of the issue is that I started using visit_annotation for these bounds. So we'd queue up the bound in the list of deferred type parameters, then when visiting, we'd further queue it up in the list of deferred type annotations... Which we'd then never visit, since deferred type annotations are visited before deferred type parameters.

Anyway, the better solution here is to use a dedicated flag for these, since they have slightly different behavior than type annotations.

I've also fixed what I think is a bug whereby we previously failed to resolve Callable in:

type RecordCallback[R: Record] = Callable[[R], None]

from collections.abc import Callable

IIUC, the values in type aliases should be evaluated lazily, like type parameters.

Closes #8017.

Test Plan

cargo test

[charliermarsh]

Record should be undefined, but Callable should resolve.

[charliermarsh]

Both of these should be considered "used".

[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.

[zanieb]

Thanks for fixing this! I was going to look into it but ya beat me to it (which is good because I would have been confused)