Tweaked insulated spray-on gloves (#56232)

Some tweaking and code smoothing of the spray-on gloves. The only
mechanical change is in also letting them be washed off (although it
takes a while under a shower or using a sink).

A visible message also provides better feedback.

* Make /wash a SHOULD_CALL_PARENT proc

A number of things depend on that signal being called.

* Makes suggested changes

- Adds SIGNAL_HANDLER to signal handler
- Changes name of turf variable for readability
- Reenables lighting object override of parent

code/modules/lighting/lighting_object.dm

@@ -146,6 +146,7 @@
 	return
 
 /atom/movable/lighting_object/wash(clean_types)
+	SHOULD_CALL_PARENT(FALSE) // lighting objects are dirty, confirmed
 	return
 
 // Override here to prevent things accidentally moving around overlays.