Mostly ports /tg/'s method of seeding submaps into specific z-levels.
Due to the low number of submaps present, all of the PoIs are guaranteed to spawn. As more are added, this should fix itself.
New lighting system is needed to handle updating literally 14k+ tiles whenever the sun moves. The straight port seems to have had no adverse effects from what I could see. Don't know if it's more performant but it doesn't seem to be less.
I didn't expect the latter would be needed for the former.
* Based on https://github.com/tgstation/tgstation/pull/25386
* Create macro for defining new subsystem types.
* Create PreInit proc to handle setup that needs to be done before the map loads
* Rename garbage_controller subsystem to garbage so it matches its global SSgarbage variable name.
