[lib] introduced action field to reaction type

Summary:
introduced action field to the reaction type. action is an enum that describes whether the reaction in the reaction field is being added or removed with the values add_reaction and remove_reaction from the target message. I believe this should address the concerns from yesterday's discussion about designing reactions in a more flexible way that allows us to enable multiple reactions (like slack/discord) in the future.

Linear Task: ENG-2244

Test Plan:
flow, and nothing crashes locally on native/web. also tested adding this field with the exisiting message liking infrastructure in my local stack and was able to get unsettingReaction to appear in the DB.

Reviewers: atul, tomek, ashoat, rohan

Reviewed By: atul, tomek, ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D5801