Adds Neon Carpet (#55782)

* Adds emissive carpet, adds plane support to decal element

- Adds a basic abstract/debugging emissive carpet
- Makes decals capable of supporting plane
- Adds auto-smoothing decals

* Adds simple neon carpet variations

* Adds neon carpet reagents and recipes

* Refactors emissive blockers to allow multiple layers of emissive / emissive blocking objects

- Splits the emissive and emissive blocker plane masters into several plane masters which handle different layers of emissiveness.

* Makes neon carpet tile stacks emissive

* Rearranges and docs some emissive plane masters

- Folds the overlay lighting plane master into the emissive planes since it is also used to mask the lighting plane

* Fixes null mats_per_unit stack recombining after splitting

- I think I broke this a while ago when I reworked how stacks handle materials. Whoops.
- This basically only effects carpet at the moment. Good thing I did this when I did!

* Adds neon carpets to cargo

- Adds a cargo supply crate containing a _lot_ of neon carpets for 3000 credits

* Fixes neon carpet highlights leaking through vending machines and such

- Turns out vending machines axed their own emissive blockers whenever they updated their icon because they cleared their managed_vis_overlays...
- Generic emissive blocking has been elementized and some update_overlays procs have been straightened out.

* Fixes id_arg_index for the emissive blocker element

* Commits @Rohsie's suggestions

code/game/objects/structures.dm

@@ -8,6 +8,8 @@
 	flags_ricochet = RICOCHET_HARD
 	receive_ricochet_chance_mod = 0.6
 	pass_flags_self = PASSSTRUCTURE
+	blocks_emissive = EMISSIVE_BLOCK_GENERIC
+	emissive_blocker_plane = STRUCTURE_EMISSIVE_BLOCKER_PLANE
 	var/broken = FALSE
 
 /obj/structure/Initialize()