WIP: Resolve "Add instructions or a button to set the primary email"

What does this MR do?

Consolidate UI for setting emails

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

• Dropdown scss changes possibly have unwanted side effects elsewhere, can maybe be namespaced more

Why was this MR needed?

Setting primary/notification emails was unclear

Screenshots (if relevant)

Primary and Public emails (Profile page):

Email Page

Does this MR meet the acceptance criteria?

• Changelog entry added
• 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?

Frontend part of #24910 (moved) One item from #22223 (moved)

Currently waiting on some changes in !8120