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/modules/modular_computers/computers/modular_computer/interaction.dm

@@ -369,7 +369,7 @@
 	var/mob/M = user
 	if(use_check_and_message(M))
 		return
-	if(istype(over, /obj/machinery/power/apc) && tesla_link)
+	if(istype(over, /obj/structure/machinery/power/apc) && tesla_link)
 		return over.attackby(src, M)
 	if(!istype(over, /atom/movable/screen) && !(over == src))
 		return attack_self(M)