[keyserver] Automatically make Farcaster friends Comm friends

Summary:
Instead of just creating KNOW_OF, I think we should make friendship relationships. This will be less confusing if somebody wants to add somebody to a chat, and I think it matches expectations based on how contact list sync generally works in other apps.

Depends on D11889

Test Plan: Tested the flow and confirmed that the "Add friend" was no longer showing for friends that were automatically added due to Farcaster connections

Reviewers: ginsu

Reviewed By: ginsu

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D11890