Migrate buttons in notes_helper.rb

What does this MR do and why?

• Migrate reply button in notes_helper.rb
• Add extra styles to btn-text-field make it somewhat match the Reply input on MRs/issues
  • NOTE This is more of a band-aid; this button should be removed entirely and replaced with an input like MRs etc

Screenshots or screen recordings

	Before	After
Normal
Hover

How to set up and validate locally

Go to commit

• Button -> Comment on line of code
• Button -> Reply btn

UX Paper Cuts 16.5 → Cleanup (#424403 - closed)

✂️ UX Paper Cuts 16.6 → Activity (#425468 - closed)

Related to #428191 (closed)