[lib] check timestamps before processing edit entry operation

Summary:
This checks the timestamp to ensure that an edit operation produces a no-op update if produced with a timestamp before latest updated time

Follows logic from https://phab.comm.dev/D13215

Depends on D13346

Test Plan: Not sure how to test this yet. Might manually run these with different timestamps? Unsure how I might be able to introduce a delay.

Reviewers: tomek, marcin, ashoat

Reviewed By: tomek

Differential Revision: https://phab.comm.dev/D13347