Add behavior from React repo to FabricUIManager mock

Summary:
We recently added an implementation of the native binding for UIManager (`global.nativeFabricUIManager`) in JavaScript. This brings the logic we had in that mock in the React repository so we can properly use it for testing (as integration tests instead of unit tests).

Changelog: [internal]

bypass-github-export-checks

Reviewed By: yungsters

Differential Revision: D44298377

fbshipit-source-id: 6085df93993302c2ddce7220c73e614ad6301667