Add 2FA download button

What does this MR do?

Adds a button to the page showing your 2FA codes, this button will download a text file with each code on a new line. Not finished yet, It's functionally working just fine but the JS function needs to be moved to the proper spot in the assets dir as well as making sure it conforms to the style guide. I'll try to work out where to put this but maybe some tips would be appreciated.

One thing I'm not sure about is if this :onclick => "download('#{@codes.join('\n')}')"} on the button tag is an acceptable way of handling this

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

Needs a security review before merging.

Why was this MR needed?

Fixes #47963 (closed)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated (No changes needed)
• API support added (none needed)
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style 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)