dvc: fix installation from archives

Fixes: iterative#7124

webdav: fix unstrip_protocol

fs: path: use ntpath/posixpath

This is less error-prone than implementing these methods ourselves.

build: bump s3/gcsfs from 2021.10.1 to 2021.11.0

Bumps [gcsfs](https://github.com/fsspec/gcsfs) from 2021.10.1 to 2021.11.0.
- [Release notes](https://github.com/fsspec/gcsfs/releases)
Bumps [s3fs](https://github.com/fsspec/s3fs) from 2021.10.1 to 2021.11.0.
- [Release notes](https://github.com/fsspec/s3fs/releases)
- [Changelog](https://github.com/fsspec/s3fs/blob/main/release-procedure.md)

---
updated-dependencies:
- dependency-name: s3fs
  dependency-type: direct:development
  update-type: version-update:semver-minor
- dependency-name: gcsfs
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

git: use asyncssh as dulwich SSH vendor (iterative#6797)

* git: support client kwargs for auth in remote methods

* tests: use docker for git/ssh server

* move dulwich backend into subdir

* add base sync<->async support

* dulwich: add initial asyncssh SSH vendor

* dulwich: use asyncssh as the default SSH vendor

* add test for git over ssh

* test read (fetch) over ssh

* ci: re-enable ssh tests

temporary workaround for iterative#6788, iterative#6789

* move async stubs into dvc.scm.asyn

* tests: use sshfs and not dvc.fs.ssh

* allow explicit 0-length read in asyncssh vendor

dvc: bump to 2.8.1

dvc: bump to 2.8.0

dvc: bump to 2.7.4

dvc: bump to 2.7.3

dvc: bump to 2.7.2