[native] Stop persisting messageIDs in messageStore.threads

Summary:
Revision for task ENG-1430.

We do want to stop persisting messageIDs since they can be deterministically generated based on SQLite output (and we already do it in code).
Transformation is needed to provide ability to omit deeply nested fields, also, outbound function (second argument) assigns an empty array to messageIDs before re-hydration because we always expect this field to be defined.

Test Plan:

1. Make some interaction on app, close, and check if on application run after persist/REHYDRATE we have empty messageIDs in state (it'll mean that data stopped being persisted)
2. Close app, kill keyserver and run app (to make sure we interact only with SQLite) to check if messages and threads were computed properly.

Reviewers: tomek, atul, abosh

Reviewed By: tomek

Subscribers: ashoat, atul, abosh

Differential Revision: https://phab.comm.dev/D5001