Improve the request / withdraw access button

What does this MR do?

It implements the design proposed in #18310 (closed).

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

No.

Why was this MR needed?

To close #18310 (closed).

What are the relevant issue numbers?

Closes #18310 (closed).

Screenshots

Group access request

Request button

Medium	Large

Withdraw request button

Medium	Large

Project access request

Request button

Medium	Large

Withdraw request button

Medium	Large

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• Tests
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together