Add drag handle to block groups

[bjarnef]

In block groups can we add a drag handle for consistency?
The group header can of course be dragged, but the handle indicates the element is draggable.

In Umbraco 13 we had it, although only shown on hover.
Furthermore it may be better to shown remove button as in prevalues for color picker, dropdown etc. as it currently is difficult seeing the remove button has focus, when navigating via keyboard.