consistent size, padding and margins for mr widget buttons

What does this MR do?

• Style all .btns inside .mr-widget to be either 30px or 25px tall
• remove redundant rules, group some btn rules together

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

Why was this MR needed?

Screenshots (if relevant)

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?

Most of #33087 (closed) should be fixed

Fixes #33970 (closed) Fixes #33972 (closed) Fixes #33973 (closed) Fixes #33974 (closed)