Simplify _bind_draw_path_function.

[anntzer]

It doesn't actually need to be a context manager, but can be a plain
function, with an easier to explain behavior.

PR Summary

PR Checklist

Tests and Styling

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs should build without error).

[jklymak]

So its OK now for self._dpi_cor to be changed permanently here?

[anntzer]

It was already set permanently before?

[timhoffm]

Optional: What do you think of introducing

_DrawPathArgs = namedtuple('_DrawPathArgs', 'path, transform, rgb_face')

The main motivation is to name the tuple elements because the function signature
where we could look up their meaning is quite far away.

With this we could write:

Suggested change

	path = self.get_path()
	transform = self.get_transform()
	tpath = transform.transform_path_non_affine(path)
	affine = transform.get_affine()
	self._draw_paths_with_artist_properties(
	renderer,
	[(tpath, affine,
	# Work around a bug in the PDF and SVG renderers, which
	# do not draw the hatches if the facecolor is fully
	# transparent, but do if it is None.
	self._facecolor if self._facecolor[3] else None)])
	transform = self.get_transform()
	self._draw_paths_with_artist_properties(
	renderer,
	[_DrawPathArgs(
	path=transform.transform_path_non_affine(self.get_path),
	transform=transform.get_affine(),
	# Work around a bug in the PDF and SVG renderers, which
	# do not draw the hatches if the facecolor is fully
	# transparent, but do if it is None.
	rgb_face=self._facecolor if self._facecolor[3] else None),
	])

[anntzer]

I switched to using a dict (and **kwargs unpacking), which seems just as good here.

[anntzer]

Actually #23571 (comment) doesn't really work because the parameter names are not part of the backend API; indeed, patheffects renderers use different parameter names. So really these arguments are currently positional and I reverted to the previous (tuple-based) approach.
We could consider making the parameter names part of the API, but that would mean a deprecation dance around patheffects (which I don't really want to do right now) and could also cause breakage for third-party backends which can be quite annoying to check for (something like replacing calls to draw_path(**kwargs) by try: draw_path(*kwargs) except TypeError: warn(); draw_path(*args); note that checking the function signature may explicitly not work for backends written as extension modules).

[timhoffm]

Ok, let's not overengineer this. You can self-merge when green.