[native] Move avatar-related components to native/avatars
Summary: Very straightforward drag and drop. Just makes things easier to work with when they're all in one avatars directory instead of in components which has a ton of files.
Test Plan: Flow/ESLint
Reviewers: ashoat, ginsu
Reviewed By: ginsu
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D7490