Cube Query Rendering - Improve panel responsiveness and consistency

Problem to solve

There are three visualisations needed to build out the preview dashboards:

• Cube Query Rendering Widget - Table (#382910 - closed)
• Cube Query Rendering Widget - Line Chart (#377708 - closed)
• Cube Query Rendering Widget - Single Stat (#382909 - closed)

The problem is that each visualisation has noticeable differences in spacing and responsiveness relative to its containing panel.

Proposal

• Ensure that all 3 visualisations have consistent spacing inside their panel container.
• Ensure that all 3 visualisations are fully responsive inside their panel container and don't leave any unused empty state.

Implementation plan

Update the styles for all three visualisations.