Resolve "Improve project overview UI" - buttons

What does this MR do?

• Restyle currently smaller-than-default buttons to use default padding
  • Since Project and Group overview pages share the same styles, the buttons on Group Overview are also updated as part of an imminent redesign
• Star and Fork controls replaced with same styling as issue count badges in Issue Boards feature
• The buttons that will remain in this row are:
  • Star
  • Fork
  • Clone
  • Notifications level
  • Request access / Leave project
• The Download and Add buttons are removed

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

That the removed HAML and CSS rules aren't going to cause a problem somewhere else 😄

Why was this MR needed?

See #44704 (closed)

Screenshots (if relevant)

Project Overview, Desktop	Project Overview, Mobile

Group Overview

Does this MR meet the acceptance criteria?

• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #44704 (closed)