[web] Add message search context

Summary:
issue: https://linear.app/comm/issue/ENG-3466/add-some-state-for-keeping-the-search-query
We want to be able to remeber the query the user has typed in, for each chat.

Test Plan: Tested with subsequent diffs

Reviewers: kamil, kuba, michal, tomek

Reviewed By: tomek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8272