Enterprise home: Create basic common lightweight panel component

Created by: limitedmage

Create basic common lightweight panel component with header, optional settings button, optional extra toolbar buttons, and three states: loading, empty, displaying content (no settings). Create dummy panels for each of the four panels in the home page under the feature flag.

Settings can be implemented later when needed, as no panel will need settings for the initial MVP.

Blocked on #13418 (closed)