Design refresh: Branch/Tag/Commit selector + Repository selector

Created by: umpox

Overview

• Update styling and colors on Branch/Tag/Commit selector
• Update to a controlled popover and add dismiss icon
• Update GitReferenceNodes to use badge styles across app

Design issue: https://github.com/sourcegraph/sourcegraph/issues/19927

Screenshots

Branch/Tag/Commit Selector

Repository selector

Designs: https://www.figma.com/file/NIsN34NH7lPu04olBzddTw/Design-Refresh-Systemization-source-of-truth?node-id=954%3A1976

Still to come (Other PRs)

• Search contexts selector
• Show more changes