[lib] introduced ReactionMessageInfo

Summary:
introduced ReactionMessageInfo to message types. This type will be needed in our Reaction Message Spec

Linear Task: ENG-2243

Test Plan: Flow and this will be further tested in subsequent diffs

Reviewers: atul, rohan

Reviewed By: atul

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D5683