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/effects/decals/cleanable/misc.dm

@@ -105,6 +105,7 @@
 	desc = "Somebody should remove that."
 	gender = NEUTER
 	layer = WALL_OBJ_LAYER
+	plane = GAME_PLANE_UPPER
 	icon_state = "cobweb1"
 	resistance_flags = FLAMMABLE
 	beauty = -100

code/game/objects/effects/decals/misc.dm

@@ -19,6 +19,7 @@
 	icon = 'icons/obj/chempuff.dmi'
 	pass_flags = PASSTABLE | PASSGRILLE
 	layer = FLY_LAYER
+	plane = ABOVE_GAME_PLANE
 	///The mob who sourced this puff, if one exists
 	var/mob/user
 	///The sprayer who fired this puff