[native] Add second register button only visible to devs

Summary:
The second register button currently does the same thing that the old one does, but in the next diffs I'll start to differentiate it.

Depends on D7494

Test Plan:

before	after (__DEV__)	after (!__DEV__)

("before" and "after (!__DEV__)" should look identical)

Reviewers: ginsu, atul

Reviewed By: ginsu

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7495