[lib] Update UPDATE_RELATIONSHIP.rawMessageInfoFromServerDB to handle farcaster_mutual

Summary:
Include creatorFID and targetFID in returned RawUpdateRelationshipMessageInfo

Depends on D11651

Test Plan:
Will log value of RawUpdateRelationshipMessageInfo at callsite when operation is farcaster_mutual and ensure that it looks as expected.

Will also be tested implicitly by the rest of the stack.

Reviewers: ginsu, tomek, will, varun

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11652