Fix 3D moving platform logic

Same thing that was already done in 2D, applies moving platform motion
by using a call to move_and_collide that excludes the platform itself,
instead of making it part of the body motion.

Helps with handling walls and slopes correctly when the character walks
on the moving platform.

Also made some minor adjustments to the 2D version and documentation.

Co-authored-by: fabriceci <fabricecipolla@gmail.com>

modules/bullet/godot_result_callbacks.cpp

@@ -135,6 +135,10 @@ bool GodotKinClosestConvexResultCallback::needsCollision(btBroadphaseProxy *prox
 			if (m_self_object->has_collision_exception(gObj) || gObj->has_collision_exception(m_self_object)) {
 				return false;
 			}
+
+			if (m_exclude->has(gObj->get_self())) {
+				return false;
+			}
 		}
 		return true;
 	} else {