Fix rasterio rowcol operation return type

[ryux1]

Closes #16342.

Preserve the default integer result while propagating a custom operation's return type through rowcol and index.

Agent used: OpenAI Codex.

[thomas-maschler]

I don't think all the extra @overload functions are necessary here.

Use _T = TypeVar("_T", default=int)

and for the existing rowcol() use

op: _RoundOperation[_T] | None = None and return tuple[_T, _T] | tuple[list[_T], list[_T]]

You can remove all the extra overloads. This should address the issue.

[thomas-maschler]

No need to include tests

[ryux1]

Updated to use a defaulted type variable and removed the extra overloads as suggested. I also applied the same simplification to TransformerBase.rowcol; the existing deprecated overload is retained only for the precision parameter. The full targeted stubs/rasterio test suite passes locally.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉