OverlayDrawer: Supports Mouse resize

When enabled, sidebars that are done with drawers, can be resized with the mouse between a given minimum and maximum size.

Resize is supported on drawers from all 4 edges.

For retrocompatibility, the feature is off by rdefault, it can be enabled with the property interactiveResizeEnabled.

It is resposibility of the application implementation to save and restore the size.

Supports plasma/discover!1128 (merged) and plasma/plasma-systemmonitor!376 (merged)