Onboarding V4 - Hetzner

How does this PR change the system?
This PR updates the onboarding flow to support Hetzner

It also revamps and refactors the onboarding flow code to make adding new providers even simpler

Out of Scope:
This PR does not yet expand onboarding to include Digital Ocean.

How was it tested?
Ran through the onboarding for each provider successfully!

Double checked all the copy and design.

Author: wendybujalski