dvc.fs.Path.parts includes sep after drive letter for windows style

[jonburdo]

When using windows style paths, we get the sep between the drive and the rest of the path:

Path('\\').parts('c:\\a')

('c:', '\\', 'a')

We should really get this result I think:

Path('\\').parts('c:\\a')

('c:', 'a')

Note this is still a little different from pathlib, which would include the sep with the drive:

from pathlib import PureWindowsPath
PureWindowsPath('c:\\a').parts

('c:\\', 'a')

but this is probably more in-line with fsspec, which basically treats the drive letter as the first element of a relative path:

fsspec.AbstractFileSystem._parent('c:/a')

'c:'

version info:

DVC version: 2.9.4.dev28+gd90fe54d.d20220106 
---------------------------------
Platform: Python 3.10.1 on Linux-5.15.11-arch2-1-x86_64-with-glibc2.33
Supports:
	azure (adlfs = 2021.10.0, knack = 0.9.0, azure-identity = 1.7.1),
	gdrive (pydrive2 = 1.10.0),
	gs (gcsfs = 2021.11.1),
	hdfs (fsspec = 2021.11.1, pyarrow = 6.0.1),
	webhdfs (fsspec = 2021.11.1),
	http (aiohttp = 3.8.1, aiohttp-retry = 2.4.6),
	https (aiohttp = 3.8.1, aiohttp-retry = 2.4.6),
	s3 (s3fs = 2021.11.1, boto3 = 1.19.8),
	ssh (sshfs = 2021.11.2),
	oss (ossfs = 2021.8.0),
	webdav (webdav4 = 0.9.3),
	webdavs (webdav4 = 0.9.3)
Cache types: <https://error.dvc.org/no-dvc-cache>
Caches: local
Remotes: https
Workspace directory: btrfs on /dev/mapper/nvme0n1p3_crypt
Repo: dvc, git