[lib][native] Introduce FarcasterDataHandler

Summary: This component will eventually handle querying Neynar when the app starts and creating threads with connections.

Test Plan: This was tested during the Hackathon to make sure it worked at app start and foreground

Reviewers: atul, ginsu

Reviewed By: ginsu

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D11387