[native] Put thread info and sourceMessageID in one object
Test Plan: Open an existing thread and send a message. Open pending thread and send a message.
Reviewers: ashoat
Reviewed By: ashoat
Subscribers: karol-bisztyga, subnub, atul, Adrian, zrebcu411, KatPo
Differential Revision: https://phabricator.ashoat.com/D727