Evaluate default parameter value in enclosing scope (#12852)
## Summary
This PR fixes a bug in the semantic model where it would evaluate the
default parameter value in the type parameter scope. For example,
```py
def foo[T1: int](a = T1):
pass
```
Here, the `T1` in `a = T1` is undefined but Ruff doesn't flag it
(https://play.ruff.rs/ba2f7c2f-4da6-417e-aa2a-104aa63e6d5e).
The fix here is to evaluate the default parameter value in the
_enclosing_ scope instead.
## Test Plan
Add a test case which includes the above code under `F821`
(`undefined-name`) and validate the snapshot.
