phorge: Replace `fab` library with local client
Replace the https://pypi.org/project/fab/ Phabricator API library with a local wikibugs2.phorge.ConduitClient class. This class is a thin wrapper around the https://pypi.org/project/requests/ library.
Advantages over the prior fab library:
- Uses requests.Session to enable HTTPS session pooling.
- Sets connect and read timeouts
- No need to wonder how
import phabricator
works
Bug: T359145