Create project: Migrate a first step to vue

What does this MR do and why?

• Add a new_project_creation_form feature flag
• Migrate a first step of a project creation form to vue

⚠️⚠️⚠️ These changes are behind the new_project_creation_form feature flag. They won't be available to users until all the work is done. See the plan here #514700 (closed) ⚠️⚠️⚠️

Screenshots or screen recordings

Before	After
CleanShot_2025-01-23_at_14.09.39	CleanShot_2025-01-23_at_14.08.56

How to set up and validate locally

1. In rails console enable the experiment fully

   Feature.enable(:new_project_creation_form)

2. Go to http://gdk.test:3000/projects/new
3. You can also try to go to any group you own
4. Click the [+] button on top of the sidebar
5. Click In this group > New project/repository

Links

Project creation plans: #514700 (closed)

Milestone planning issue: #499697 (closed)