Warn against use of `.__annotations__` (in many circumstances)

[JelleZijlstra]

Summary

Directly using the .__annotations__ attribute of an object is unsafe in a few circumstances:

• On classes with custom metaclasses, various odd things can happen (https://peps.python.org/pep-0749/#pre-existing-bugs). On Python 3.14 and newer this only happens if at least one of the classes involved uses from __future__ import annotations; on earlier versions it can always happen.
• Accessing __annotations__ on an instance of an annotated class works in released versions of Python (most of the time) but won't work in Python 3.14.
• (Minor) Accessing __annotations__ on arbitrary type objects will raise AttributeError on static types, e.g. int.__annotations__.

However, it is always safe to access __annotations__ on function and module objects.

Therefore, it probably makes sense for Ruff to warn against any use of the .__annotations__ attribute, perhaps with an exception for objects known to be functions or modules.

Similar to #17853.