[native] Prevent user from leaving RegistrationTerms during registration request

Summary:
This addresses ENG-7677.

We want to prevent the user from dismissing RegistrationTerms during an ongoing registration request because otherwise, they can re-enter it and trigger a second registration request.

Depends on D11848

Test Plan:

1. I applied this patch, which adds a 10s wait before registration attempts, and forces keyserver auth to fail
2. I then testing the behavior in the UI. See video below

Reviewers: varun

Reviewed By: varun

Subscribers: inka, tomek

Differential Revision: https://phab.comm.dev/D11849