Summary:
Similar to #21950, this adds displayName to `ActivityIndicator`, so it displays the correct component name in snapshots instead of `Component`.
Fixes#21937 (a little bit more than it was already fixed).
Pull Request resolved: https://github.com/facebook/react-native/pull/22417
Differential Revision: D13205376
Pulled By: TheSavior
fbshipit-source-id: 21e71d4980d159a1f33d32d83346b48257ec21d4
