Materials Repath (#22388)

Soft-ish port of https://github.com/NebulaSS13/Nebula/pull/540. Except
we call them singletons.

Repaths all materials as singletons instead of datums, and replaces
material defines from strings to paths so that we can just run
GET_SINGLETON instead of needing to use SSMaterials. This is Step One.

This PR has no player-facing changes.

changes:
  - refactor: "Repaths /material to /singleton/material."
- refactor: "Replaces all material string defines to path defines,
replacing SSmaterials procs w/ GET_SINGLETON instead."
- refactor: "Removes all material var edited objects from all maps,
adding new presets where necessary."
- refactor: "Updates recipes unit test to run all recipes against all
material singletons."

---------

Signed-off-by: Batrachophreno <Batrochophreno@gmail.com>
Co-authored-by: kano-dot <bhutanlikanoxy@gmail.com>

code/modules/materials/material_sheets.dm

@@ -8,8 +8,8 @@
 	max_amount = 50
 	recyclable = TRUE // Pretty much all materials should be recyclable
 
-	var/default_type = DEFAULT_WALL_MATERIAL
-	var/material/material
+	var/default_type = MATERIAL_STEEL
+	var/singleton/material/material
 	var/perunit
 	var/apply_colour //temp pending icon rewrite
 	var/painted_colour
@@ -25,8 +25,8 @@
 	randpixel_xy()
 
 	if(!default_type)
-		default_type = DEFAULT_WALL_MATERIAL
-	material = SSmaterials.get_material_by_name(default_type)
+		default_type = MATERIAL_STEEL
+	material = GET_SINGLETON(default_type)
 	if(!material)
 		return INITIALIZE_HINT_QDEL
 
@@ -81,7 +81,7 @@
 
 /obj/item/stack/material/transfer_to(obj/item/stack/S, var/tamount=null, var/type_verified)
 	var/obj/item/stack/material/M = S
-	if(!istype(M) || material.name != M.material.name)
+	if(!istype(M) || material.type != M.material.type)
 		return 0
 	var/transfer = ..(S,tamount,1)
 	if(src)
@@ -285,7 +285,7 @@
 /obj/item/stack/material/steel
 	name = DEFAULT_WALL_MATERIAL
 	icon_state = "sheet-metal"
-	default_type = DEFAULT_WALL_MATERIAL
+	default_type = MATERIAL_STEEL
 	icon_has_variants = TRUE
 
 /obj/item/stack/material/steel/attackby(obj/item/attacking_item, mob/user)
@@ -562,7 +562,7 @@
 /obj/item/stack/material/bronze
 	name = "bronze"
 	icon_state = "sheet-brass"
-	default_type = "bronze"
+	default_type = MATERIAL_BRONZE
 	icon_has_variants = TRUE
 
 /obj/item/stack/material/bronze/full/Initialize()