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/spell_system/artifacts/items/bone_spear.dm

@@ -1,3 +1,3 @@
 /obj/item/material/twohanded/spear/bone
 	desc = "A spear crafted with bones of some long forgotten creature."
-	default_material = "cursed bone"
+	default_material = MATERIAL_BONE_CURSED