[web] Fetch loggedInUserInfo in ThreadListProvider

Summary:
This diff should be a no-op. In a later diff, we'll need to pass loggedInUserInfo directly to getThreadListSearchResults.

I also introduce a small hook here: useLoggedInUserInfo.

Test Plan: Flow, and playing around with inbox on web

Reviewers: atul

Reviewed By: atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D6753