Sometimes gizmos may be covering items underneath which the user intends to select:
It should be possible to click over a Gizmo to select items underneath it.
We can solve this by differentiating between a click and a drag, just like we do outside the gizmos.
To make this work well, we need to change the input, so that the drag threshold is more reasonable for mouse and trackpad input.
This requires us to add separate drag thresholds for Mouse, Pen and Keyboard.