gh-135801: Improve filtering by module in warn_explicit() without module argument...

gh-135801: Improve filtering by module in warn_explicit() without module argument (GH-140151)

* Try to match the module name pattern with module names constructed
  starting from different parent directories of the filename.
  E.g., for "/path/to/package/module" try to match with
  "path.to.package.module", "to.package.module", "package.module" and
  "module".
* Ignore trailing "/__init__.py".
* Ignore trailing ".pyw" on Windows.
* Keep matching with the full filename (without optional ".py" extension)
  for compatibility.
* Only ignore the case of the ".py" extension on Windows.