Update label styling

What does this MR do and why?

• Use Pajamas design
• Fix labels in bulk edit and quick actions

What does this MR not do?

• completely fix the bulk edit epics dropdown (why does it look so different? 🤔)

Screenshots or screen recordings

	Before	After
Sidebar dropdown
Bulk edit
Quick action

How to set up and validate locally

• Look at labels dropdown in issue/MR/etc
• Look at dropdown in bulk edit sidebar on issues/MRs
• Use /label quick action

#398228 (closed)