Changing the collision layer of a sleeping body was not triggering area
updates correctly.
Bodies need to be active for collision to be checked against already
overlapping bodies and areas.
Neighbors need to be activated too in order to handle the case where a
static body is modified (it can't be activated directly but paired
bodies need to check their collision again).
In 3D, moved the call to wakeup() from the physics server to
GodotBody3D::_shapes_changed to make it consistent with 2D and also
handle the case where shapes are modified (_shapes_changed is called in
both this case and collision layer changes).
