[native] Replace OptimisticThreadInfo with ThreadInfo in camera modal

Summary: The same as in D1143, we can replace OptimisticThreadInfo

Test Plan: Create realized thread by sending an image using camera modal

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: KatPo, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D1144