Refactor google cloud form

What does this MR do and why?

Small refactor to align with new UX changes for GCP. Follow up from !142863 (merged)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

How to set up and validate locally

1. Enable flag :gcp_runner
2. Visit project and group runner creation views (not available on admin)
3. Select google cloud radio option
4. Test out UI (static for now)
5. Ensure runner creation still works with flag off when selecting previous platform options