Summary:
Minimal set of changes to intercept events in external modules. Current intended use-case is for Reanimated to handle events for the Animated properties.
Changelog: [Added] Add listeners to allow intercepting events in C++ core.
Reviewed By: cipolleschi
Differential Revision: D35312534
fbshipit-source-id: ec924b57fd0c0dabf7be7b886dbef23bf3170d6c