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.
