Can resolve methods in nested classes

[chbndrhnns]

Fixes https://youtrack.jetbrains.com/issue/PY-71963/Jump-to-source-from-test-panel-fails-when-using-nested-classes

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Note

Enables resolving nested classes and their methods during qualified name lookup and adds tests covering inner/nested class scenarios in PyTestsLocator.

• Resolution logic (QualifiedNameExt.kt):
  • Enhance QualifiedName.getElementAndResolvableName to resolve nested PyClass hierarchies and locate methods within nested classes (including multi-level nesting), with fallback to current class method lookup.
• Tests:
  • Add PyTestsLocatorTest covering:
    • Method in top-level class (test_.Test.test_1).
    • Resolving inner class (test.TestOuter.TestInner).
    • Method in inner class and in multi-level nested classes (...TestInner.test_1).

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[chbndrhnns]

Rebased onto 251.
@EliseevEgor Do you need anything else from me?

[chbndrhnns]

@EliseevEgor @BartvHelvert This has been untouched for three months now. May I ask for an update?

[missingdays]

@chbndrhnns thanks a lot for your contribution!

Some of your changes are not covered by the new tests. Could you please add new tests to cover them?

[chbndrhnns]

I updated the PR.

[missingdays]

@chbndrhnns Thank you!
I merged the PR using our internal infrastructure and closed the related ticket.
Thanks again for your contribution.