R1:288498f8d099

Add conduit.getcapabilities and a modern CLI handshake workflow

Summary:
Ref T5955.

- Add `conduit.getcapabilities` to help arc (and other clients) determine formats, protocols, etc., the server supports.
- Fixes T3117. Add a more modern version of the handshake workflow that allows all generated tokens to remain valid for an hour.
- Generally, add a CLI token type. This token type expires after an hour when generated, then becomes permanent if used.

Test Plan:
- See D10988.
- Ran `conduit.