[native] Remove ChatThreadList class component

Summary:
This diff finally removes the ChatThreadList class component altogether.

That said, this functional component is still cluttered and hasn't been optimized. I will work to declutter ChatThreadList and improve performance in subsequent diffs.

Depends on D9190

Test Plan: Everything continues to work as expected/before!

Reviewers: ginsu, tomek, rohan

Reviewed By: ginsu

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D9191