Migrate forks button from HAML to Vue

What does this MR do and why?

This MR migrates the fork button on the project overview page from HAML to Vue 🙂

Screenshots or screen recordings

No visual changes, the fork button looks the same before and after this MR 🙂

How to set up and validate locally

It is tricky to validate all possible states of the button 😅

• Choose a project
• Impersonate a user that has not forked the project
  • The fork button should be a link to the new fork page
    • If the project has forking disabled, the fork button should be disabled
    • If the user has reached the limit of projects it can create, the fork button should be disabled
• Impersonate a user that has already forked the project
  • If the user has access to only its own namespace (no write access to other groups) the fork button should be a link to its own fork
  • If the user has access to multiple namespaces (so write access to at least one other group) the fork button should be a link to the new fork page
    • If the project has forking disabled, the fork button should be disabled
    • If the user has reached the limit of projects it can create, the fork button should be disabled

The forks count button is always a link to the project forks page.

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.

Related to #415360