[CommCoreModule] implement ops for message store threads

Summary:
C++ version of message ops introduced in D7396.

Message IDs are not needed - can be computed based on Messages table.

Depends on D7468

Test Plan: Run some mock operations and check if they modify table properly.

Reviewers: tomek, marcin

Reviewed By: tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7469