Accessibility improvements to message drawer

Improve accessibility of the new message drawer

E.g.

• Add aria labels for cancel edit message button (the little cross when selecting messages)
• Add better aria labels to the menus in messaging (simply saying "Info" doesn't give the user any context)
• Add better contrast levels to hovering of messages or perhaps even change how that works
• Keyboard navigation of messages (up/down)
• messages can be focused when a dialogue is open