Resolve "Inconsistent location of members page between groups and projects"

What does this MR do?

It moves the project members page from the settings to the main project menu. For that i reactivated an already

Are there points in the code the reviewer needs to double check?

Backend Controller needs to be rechecked, haven't rewritten anything but moved controller code from the settings route over to the already existing project_members route

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #29893 (closed)