Fixes layering issues brought by the FoV PR. (#63903)

* Fixed most (not all) incorrect planes and layers detected by the unit test.

code/game/objects/structures/shower.dm

@@ -113,6 +113,7 @@
 		return
 	var/mutable_appearance/water_falling = mutable_appearance('icons/obj/watercloset.dmi', "water", ABOVE_MOB_LAYER)
 	water_falling.color = mix_color_from_reagents(reagents.reagent_list)
+	water_falling.plane = GAME_PLANE_UPPER
 	. += water_falling
 
 /obj/machinery/shower/proc/handle_mist()
@@ -211,6 +212,7 @@
 	icon = 'icons/obj/watercloset.dmi'
 	icon_state = "mist"
 	layer = FLY_LAYER
+	plane = ABOVE_GAME_PLANE
 	anchored = TRUE
 	mouse_opacity = MOUSE_OPACITY_TRANSPARENT