[native][web] Fix timestamp type in cpp

Summary:
issue: ENG-8893
Timestamps exceed int, we need to use long long

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 this change fixed message search - next pages or results are now correctly fetched

Reviewers: tomek, kamil

Reviewed By: tomek, kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D12866