Feat: register with phone frontend

What does this MR do and why?

Implementing frontend part of registration with phone number by default and with a tab for registration with email.

Screenshots

Email	Phone

Screencast

CleanShot_2023-02-13_at_17.38.31

Describe in detail what your merge request does and why.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

1. Boot up your GDK with GITLAB_SIMULATE_SAAS=1 as environment variable.
2. Try following code in your rails console

• ApplicationSetting.first.update(phone_verification_code_enabled: true)
• Feature.enable(:registrations_with_phone)

3. Go to registration page and observe.

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.