Persist drafts in SQLite

Summary: This differential uses new CommCoreModule functionality to persist drafts in SQLite database.

Test Plan: At this point a potential test would involve dispatching appriproate redux action and examine flipper and SQLite.

Reviewers: atul, tomek

Reviewed By: atul, tomek

Subscribers: ashoat, abosh

Differential Revision: https://phab.comm.dev/D5649