[lib] Introduce shared getRelationshipDispatchAction function

Summary: Move part of the logic responsible for selecting correct RelationshipAction basing on provided RelationshipButton to lib so it could be resused on web

Test Plan: Confirm the existing logic still worrks on native

Reviewers: tomek, atul

Reviewed By: tomek

Subscribers: ashoat, adrian, abosh

Differential Revision: https://phab.comm.dev/D4677