Adopt split repo: _google-auth-library-python-httplib2_ #14909
Description
Migrate the split-repo https://github.com/googleapis/google-auth-library-python-httplib2 to https://github.com/googleapis/google-cloud-python.
The migration readiness criteria are the following, which we track via GitHub labels on this issue. These criteria apply to the split repo we are migrating from:
No open issues
No open PRs
No handwritten samples