[lib] Check the timestamps when updating read status

Summary:
Check the timestamp before setting the value. We need to use a different update type so that we can update also the timestamps.

https://linear.app/comm/issue/ENG-9120/update-thread-unread-status-spec

Depends on D13241

Test Plan: Process a couple of operations setting to read / unread.

Reviewers: kamil, inka, marcin

Reviewed By: inka

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13240