[lib] refactor thread activity reducer to use sqlite operations

Summary:
Refactor the thread activity reducer to use sqlite operations

Depends on D11576

Test Plan: Passing existing thread activity reducer tests. Actual sqlite operations are tested later in stack.

Reviewers: kamil, atul, ginsu

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11578