[lib][native] Unshim FARCASTER_MUTUAL messages on the client
Summary:
This addresses ENG-7991 and ENG-7992.
Depends on D11871
Test Plan: Tested sending a shimmed message to a client (both native and web) and confirmed it was unshimmed
Reviewers: ginsu, atul
Reviewed By: ginsu
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D11883