implement `rm -rf` in terms of pathlib

[RonnyPfannschmidt]

followup to #3988 (comment)

as it turns out shutil.rmtree is unable to be harsh
its fine if we aren't for a while, but we need eventual parity

[Zac-HD]

That is, implement the following using pathlib rather than shutil:

pytest/src/_pytest/pathlib.py

Lines 49 to 56 in dc0b4ef

	def rmtree(path, force=False):
	if force:
	# ignore_errors leaves dead folders around
	# python needs a rm -rf as a followup
	# the trick with _shutil_rmtree_remove_writable is unreliable
	shutil.rmtree(str(path), ignore_errors=True)
	else:
	shutil.rmtree(str(path))

[RonnyPfannschmidt]

also ref #4222

[gnikonorov]

I'm going to take a look at this one as I'm freeing up a bit.
@RonnyPfannschmidt - can you elaborate what you mean by shutil.rmtree is unable to be harsh? If I understand correctly, all we need to do is what @Zac-HD has suggested but I am curious about your comment

[RonnyPfannschmidt]

@gnikonorov shutil.rmtree doesn't try as hard as py.path.local does

It's basically a rm -r and we need the -f on top as well

[gnikonorov]

Thanks for confirming @RonnyPfannschmidt

[RonnyPfannschmidt]

@nicoddemus i think we can consider this fixed with #5588 merged?

[nicoddemus]

Yes, thanks!