[native] Replace OptimisticThreadInfo with ThreadInfo in keyboard state container

Summary: In D727 we introduced OptimisticThreadInfo. It appears that we can simply use threadInfo, because for realized thread it is set correctly and all the pending threads are created by createPendingThread which also sets this property

Test Plan: Create realized thread by sending a selected image

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: KatPo, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D1143