Improve API and interactivity of new tooltip
This reworks the API the `InteractiveTooltip` component so that it's more
natural to use just like other React components. You can now supply the target
component as a child and the tooltip content as a prop.
In addition, this tweaks the interactivity to keep the tooltip on screen until
you move the mouse away from the tooltip and its target.
Part of https://github.com/vector-im/riot-web/issues/9753
Part of https://github.com/vector-im/riot-web/issues/9716
