Blender Git Loki

Fix T83460: Regression in snap for measure tool

Now the gizmo is drawn only when the eventstate located in
`wm->winactive->eventstate` has not changed.

So it doesn't matter if it's "selected" or not.

This commit also removes the use of the private header "wm.h"

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D9539