Feat: Show description on hover over pivot measure and dimension list.

[mindspank]

When hovering over a dimension or measure pill in the left hand dimension/measure picker in Pivot view we should show the description of the hovered asset.

AC:

• When hovering over a measure or dimension we should show the description in a tooltip if available.
• The tooltip should show after a slight delay to avoid flickering behaviour as your mouse over items in the list.
• Ideally dock the tooltip to the right of the asset to avoid rendering outside of the available screen size.