Enable physics interpolation in all 3D demos (#1074)

This makes use of the new built-in 3D physics interpolation
added in Godot 4.4.

3d/rigidbody_character/player/cubio.gd

@@ -11,6 +11,10 @@ func _physics_process(delta: float) -> void:
 		# Pressed the reset key or fell off the ground.
 		position = start_position
 		linear_velocity = Vector3.ZERO
+		# We teleported the player on the lines above. Reset interpolation
+		# to prevent it from interpolating from the old player position
+		# to the new position.
+		reset_physics_interpolation()
 
 	var dir := Vector3()
 	dir.x = Input.get_axis(&"move_left", &"move_right")

3d/rigidbody_character/project.godot

@@ -84,6 +84,7 @@ exit={
 
 common/physics_ticks_per_second=120
 3d/default_gravity=13.0
+common/physics_interpolation=true
 
 [rendering]