Incorrect error handling when compiler_set_qualname fails

[iritkatriel]

compiler_set_qualname is called at the end of _PyCompile_EnterScope, after the compiler entered the scope. If it fails, _PyCompile_EnterScope returns error (without reverting the scope entry) and the caller would assume that there was no change in scope.

Linked PRs

• gh-156459: Fix cleanup on error in compiler_set_qualname #156461
• gh-156459: Fix cleanup on error in compiler_set_qualname #156462
• [3.15] gh-156459: Fix cleanup on error in compiler_set_qualname (GH-156462) #156574
• [3.14] gh-156459: Fix cleanup on error in compiler_set_qualname (GH-156462) #156575