feat: add compass shell progress indicator COMPASS-4515

[Anemy]

Adds a Command in Progress... indicator while a command is in progress and the shell is collapsed.
Couple other changes:

• Tweaks to the styles of the header text.
• Updated the loader indicator - different color and animation.
• Keep the shell mounted when collapsed so we avoid reloading react-ace and also can keep using the component coupled with the runtime (set state doesn't blow up when collapsed).

operation.in.progress.mp4