Update demos for Godot 4.4

- Resave all files with Godot 4.4 to make use of script/shader UIDs.
- Use AgX tonemapping in all demos that used a tonemapper other than Linear.

3d/physics_tests/utils/system.gd.uid

@@ -0,0 +1 @@
+uid://bau7sgdbs7a8y