Implement rich tooltips on debug toggle buttons

[tomgilder]

Tracker item for implementing tooltips on debug toggle buttons

• Tooltips text is being reviewed on Google Doc proposal
• Also discussion here: Debug toggle buttons redesign proposal #3144

Implementing will use existing HoverCardTooltip.

Currently the tooltips are centred below the buttons, as per Material spec:

If there's not enough space, they position like this:

...but I'd love to know thoughts on the positioning, personally I prefer aligned to the left side:

PR coming soon, have held off to avoid conflicts with renaming and icons