Move Python type stubs into bindings/python/libtorrent

[qstokkink]

libtorrent version (or branch): master

While creating the fixes of #7688, I spotted one optimization to the current directory structure: the Python type stubs can be moved from bindings/python/install_data/libtorrent into bindings/python/libtorrent.

This change would obsolete the following code in its entirety.

libtorrent/bindings/python/setup.py

Lines 506 to 513 in 7c698d8

	# Our stubs end up in the "libtorrent" directory in the wheel.
	# Setuptools expects it to exist beforehand.
	if not os.path.exists("libtorrent"):
	os.mkdir("libtorrent")
	try:
	shutil.copytree("install_data/libtorrent", "libtorrent")
	except FileExistsError:
	pass

Even though the code above can be removed, all paths that point to install_data would have to be updated.

[qstokkink]

Fixed in #7691