[native] Rename RegistrationContainer to RegistrationContentContainer
Summary:
Going to introduce RegistrationButtonContainer in the next diff, so figured it made sense to rename RegistrationContainer for consistency / to reduce ambiguity.
Depends on D7826
Test Plan: Flow
Reviewers: ginsu, atul
Reviewed By: ginsu
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D7829