gh-103193: Improve getattr_static test coverage

[AlexWaygood]

Currently, no tests would fail if we were to apply this optimisation to getattr_static, which makes things a fair bit faster:

--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1780,13 +1780,9 @@ def trace(context=1):


 def _check_instance(obj, attr):
-    instance_dict = {}
-    try:
-        instance_dict = object.__getattribute__(obj, "__dict__")
-    except AttributeError:
-        pass
-    return dict.get(instance_dict, attr, _sentinel)
-
+    if hasattr(obj, "__dict__"):
+        return dict.get(obj.__dict__, attr, _sentinel)
+    return _sentinel

However, the optimisation would lead to incorrect behaviour. test_custom___getattribute__, added in this PR, would correctly fail if the incorrect optimisation were applied.

• Issue: Optimise inspect.getattr_static #103193

[miss-islington]

Thanks @AlexWaygood for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[miss-islington]

Sorry @AlexWaygood, I had trouble checking out the 3.11 backport branch.
Please retry by removing and re-adding the "needs backport to 3.11" label.
Alternatively, you can backport using cherry_picker on the command line.
cherry_picker 921185ed050efbca2f0adeab79f676b7f8cc3660 3.11

[miss-islington]

Thanks @AlexWaygood for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[bedevere-bot]

GH-104290 is a backport of this pull request to the 3.11 branch.