[keyserver][lib][web][native] use local search for thick threads

Summary: issue: ENG-8653

Test Plan:
Tested by commenting out isThreadThin check, and commenting out extractKeyserverIDFromIDOptional(messageInfo.threadID) check in getMessageSearchStoreOps. This allowed me to treat a thin thread as if it were thick, and execute local search on it.

Tested that the messages are fetched, ordered by timestamp descending. Tested that in thin threads (if the above hacks are removed) search works as before.

One thing that doesn’t work in thick threads is fetching next pages of results. This is because timestamps exceed cpp int, so SQLiteQueryExecutor::searchMessages doesn’t bind them to sql query correctly. Fixing this is tracked in ENG-8893

Reviewers: tomek, kamil

Reviewed By: tomek, kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D12865