[lib] Update updateRelationshipInputValidator to be union of [traditional/farcaster]RelationshipRequestValidator

Summary:
Update this validator so it supports requests of type TraditionalRelationshipRequest and FarcasterRelationshipRequest

Also renamed updateFarcasterRelationshipInputValidator to farcasterRelationshipRequestValidator for clarity and more consistent naming.

Depends on D11611

Test Plan: Send both TraditionalRelationshipRequest and FarcasterRelationshipRequest requests and ensure that they are validated by keyserver. Confirmed with log statements.

Reviewers: ginsu, tomek, varun, will

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11612