Repath obj/machinery to obj/structure/machinery [MDB Ignore] (#22500)

Repaths obj/machinery to obj/structure/machinery. **Note for
reviewers:** the only meaningful changed code exists within
**code/game/objects/structures.dm** and
**code/game/objects/structures/_machinery.dm**, largely concerning
damage procs. With the exception of moving airlock defines to their own
file, ALL OTHER CHANGES ARE STRICTLY PATH CHANGES.

Objects, _categorically_, are largely divided between those you can hold
in your hand/inventory and those you can't. Machinery objects are
already subtypes of Structures behaviorally, this PR just makes their
pathing reflect that, and allows for future work (tool actions, more
health/destruction functionality) to be developed without unnecessary
code duplication.

I have tested this PR by loading up the Horizon and dismantling various
machines and structures with tools, shooting guns of various types
throughout the ship, and detonating a bunch of explosions throughout the
ship.

code/controllers/subsystems/processing/shuttle.dm

@@ -73,7 +73,7 @@ SUBSYSTEM_DEF(shuttle)
 	entry_points_to_initialize.Cut()
 
 /datum/controller/subsystem/shuttle/proc/initialize_ship_weapons()
-	for(var/obj/machinery/ship_weapon/SW in weapons_to_initialize)
+	for(var/obj/structure/machinery/ship_weapon/SW in weapons_to_initialize)
 		SW.sync_linked()
 		if(SW.linked)
 			LAZYADD(SW.linked.ship_weapons, SW)