[lib] Introduce setMessageStoreMessages redux action

Summary: To be dispatched from sqlite-context-provider in future diffs to restore messageStore.messages persisted in SQLite.

Test Plan: Will be tested with subsequent diffs.

Reviewers: palys-swm, def-au1t, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, Adrian, karol-bisztyga, benschac, boristopalov

Differential Revision: https://phabricator.ashoat.com/D2599