Always show ExpandableListitem buttons, not just on hover
Hover buttons suffer from discoverability problems and can't be used on touch, and this component is explicitly trying to be touch-friendly. So let's make the buttons always be visible, not just on hover.
To avoid the appearance becoming too heavy, the Buttons are turned into ToolButtons.
simplescreenrecorder-2020-11-04_13.30.52
But if people think the raised pushbutton style would be okay, I can go back to that.
BUG: 428624 FIXED-IN: 5.76
cc @teams/vdg