[keyserver] Update createPersonalThreads to support both [Traditional/Farcaster]RelationshipRequest

Summary:
Now that we may get userIDsToFID instead of userIDs, we need to transform back to list of userIDs via Object.keys to maintain existing behavior.

Depends on D11606

Test Plan:

1. Set breakpoints and add log statements to ensure that userIDs gets constructed as expected for both traditional and farcaster relationship requests.
2. Check keyserverDB to ensure that threads are created as expected

(need to go through again before landing)

Reviewers: ginsu, varun, tomek, will

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11607