[lib] Add function allowing extracting ThreadInfo from updates

Summary:
We need this later in the stack to extract updated thread info from the result of operations processing.

https://linear.app/comm/issue/ENG-8930/unify-the-approach-to-replies-count-and-unread-status-updates

Depends on D13055

Test Plan: Flow, tested with the rest of the stack.

Reviewers: kamil, inka

Reviewed By: inka

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13057