Fix bounded self types in override incompatibility checking

[hauntsaninja]

Fixes#15041

Related to #14882 and #14017 (the older one is where I added the xfail test)

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

pandas (https://github.com/pandas-dev/pandas)
+ pandas/core/series.py:3330: error: Signature of "sort_values" incompatible with supertype "NDFrame" [override]+ pandas/core/series.py:3330: note: Superclass:+ pandas/core/series.py:3330: note: @overload+ pandas/core/series.py:3330: note: def sort_values(self, *, axis: Union[int, Literal['index', 'columns', 'rows']] = ..., ascending: Union[bool, Sequence[bool]] = ..., inplace: Literal[False] = ..., kind: str = ..., na_position: str = ..., ignore_index: bool = ..., key: Optional[Callable[[Series], Union[Series, Union[Union[ExtensionArray, ndarray[Any, Any]], Index, Series]]]] = ...) -> Series+ pandas/core/series.py:3330: note: @overload+ pandas/core/series.py:3330: note: def sort_values(self, *, axis: Union[int, Literal['index', 'columns', 'rows']] = ..., ascending: Union[bool, Sequence[bool]] = ..., inplace: Literal[True], kind: str = ..., na_position: str = ..., ignore_index: bool = ..., key: Optional[Callable[[Series], Union[Series, Union[Union[ExtensionArray, ndarray[Any, Any]], Index, Series]]]] = ...) -> None+ pandas/core/series.py:3330: note: @overload+ pandas/core/series.py:3330: note: def sort_values(self, *, axis: Union[int, Literal['index', 'columns', 'rows']] = ..., ascending: Union[bool, Sequence[bool]] = ..., inplace: bool = ..., kind: str = ..., na_position: str = ..., ignore_index: bool = ..., key: Optional[Callable[[Series], Union[Series, Union[Union[ExtensionArray, ndarray[Any, Any]], Index, Series]]]] = ...) -> Optional[Series]+ pandas/core/series.py:3330: note: Subclass:+ pandas/core/series.py:3330: note: @overload+ pandas/core/series.py:3330: note: def sort_values(self, *, axis: Union[int, Literal['index', 'columns', 'rows']] = ..., ascending: Union[bool, int, Sequence[bool], Sequence[int]] = ..., inplace: Literal[False] = ..., kind: str = ..., na_position: str = ..., ignore_index: bool = ..., key: Optional[Callable[[Series], Union[Series, Union[Union[ExtensionArray, ndarray[Any, Any]], Index, Series]]]] = ...) -> Series+ pandas/core/series.py:3330: note: @overload+ pandas/core/series.py:3330: note: def sort_values(self, *, axis: Union[int, Literal['index', 'columns', 'rows']] = ..., ascending: Union[bool, int, Sequence[bool], Sequence[int]] = ..., inplace: Literal[True], kind: str = ..., na_position: str = ..., ignore_index: bool = ..., key: Optional[Callable[[Series], Union[Series, Union[Union[ExtensionArray, ndarray[Any, Any]], Index, Series]]]] = ...) -> None
pandas-stubs (https://github.com/pandas-dev/pandas-stubs)
- pandas-stubs/core/indexes/range.pyi:87: error: Unused "type: ignore" comment

[hauntsaninja]

The primer is expected (and correct), it's where the xfail test came from in the first PR

[hauntsaninja]

I'm merging this because I'm quite confident and because I want it to make 1.3 (#15075). #14975 is potentially a superset of this, but I need to find time to think through the ignore_type_vars