Labyrinthine Structures: Furniture/Terrain planning

### Is your feature request related to a problem? Please describe.

Labyrinthine Structures are proposed [subdimensional "dungeons"](https://github.com/CleverRaven/Cataclysm-DDA/issues/55794) linked to netherum and exodii content. They should become the new go-to loot area to get CBM related gear semi-independently of the exodii (connection to at least another high tech faction will be necessary to get it fully functional), as well as a new and different type of place to loot. The core of the lore is that the exodii use the mimicry properties of the Netherum to intentionally create nether-copies of their own stuff. These places are creepy and weird but can be looted.

I have been unable to devote much time to CDDA dev recently and don't have any idea when this will change, so in the interests of both getting my plans in writing for my future self and also possibly enticing someone to help me work on this, I am writing up some of the notes I have on these structures into issues to store in an associated project.

This issue will detail the "basic level" mapping objects and their function for the Structures. Eventually, there should be more than these in the Structures, with more wild and chaotic nether stuff appearing the deeper you go, but these are sufficient to form the backbone until we get further along. I'm open to other suggestions here, because here more than almost any other place it's going to be tricky to capture the kind of variability we should be seeing.

### Solution you would like.

#### Basic notes:
- New "twisting metal" floor and wall terrain resembles scrap but with spiral patterns and is indestructible, used to make map edges and some cover and decor elements. Its fallback terrain is the same as the starting terrain, so even if you somehow find a way to smash or bash it, the terrain left behind should be the one you destroyed. This stuff forms the outer edges of all maps to keep players from confusing the pocket dimension algorithms and themselves.
- Basic decor inside the Structure should be able to start with everything used in the Exodii base palettes. All exodii furniture and most existing modern-tech furniture could show up, although organic stuff should be rarer.
- Deeper into the Structure we should see some special furniture that is itself loot, such as parts for autodocs and other high-value standing machinery.

#### New furniture ideas:
- [x] "crooked shelf": This wire utility shelf looks like it was built by Salvador Dali. The shelves all appear straight and level when examined individually, but when looked at as a whole they appear tilted and run into each other. Studying it for long gives you a headache.
- [x] "bulbous machine": At first glance this just looks like an unidentified machine, but as you look closer you see what appear to be hairy, fleshy surfaces mixed among the controls. Every so often it emits a soft moan.
- [x] "fabonator": This is a perfectly ordinary fabonator, like you've seen a thousand times... before? As you look closer you can no longer recall what this thing is, and its function escapes like the memory of a dream. You find you don't want to look directly at it any longer. (Maddremor thinks we should call this a reployer)
- [x] "generator?": If you had to guess you'd say this whirring machine was an electric generator, but it looks as though a six year old drew it and then a mechanical engineer built it to spec. You can't see any easy way to deactivate it.
- [x] "spindle": Although you can't tell what this is supposed to do, it is refreshingly non-bizarre for this place: a floor-to-ceiling spire of metal and wire with electricity arcing up and down inside it, casting a cold glow on the area.
- [ ] "spiral pipe": This pipe juts from the floor into a plumbing nightmare, coiling into a tight spiral before popping back down. There is what appears to be a control panel, but it is hopelessly arcane.
- [ ] "fracterminal": A simple-appearing computer terminal at first glance, this machine's surface is covered in spiralling patterns that only grow more complex as you look deeper into them. It's quite beautiful. The screen glows like a monitor, but the display is meaningless noise and mesmerizing patterns. (Eventually interacting with these might cause a semirandom effect)
- [x] "unchair": Though you can tell this is meant to be a metal chair, the angles jut awkwardly and it appears to be bolted to the floor. You don't think you would enjoy sitting on it.
- [ ] "deskesque": If you told someone what a desk looked like, without telling them what it was for, and then gave them a hallucinogen and asked them to build one, you'd get something like this.
- [ ] "ruglike": On the surface this seems to be a carpet, but on approach, it seems to actually be some kind of mossy plant growing on the floor below. It slowly undulates in twisted, spiraling patterns. Thinking on it, you're not sure how much like a rug it really is; perhaps it belongs in another genre entirely.
- [ ] "fleshtank": The shape suggests that this is a standing tank full of pressurized gas, but it is made out of pulsing organ meat, banded with heavy straps of metal.
- [x] "Wiregrass": "Growing in shining tufts from the floor are long, luscious blades of glittering golden grass on silvery stems. They look like wild barley, but metallic, with razor-sharp leaves." Movement penalty and a risk of damage moving through. Grows on nanosand.

#### New terrain ideas:
- [x] "Noncrete floor": "This looks exactly like a concrete floor, but the surface is soft and spongey. While it is a bit fun to walk on, it's not the best surface for combat." Has a moderate movement penalty.
- [x] "nanosand": "A sandy material that seems to naturally fall into complex shapes, including triangles and spirals."
- [ ] "bulging wall": "The scrap metal wall here abruptly bulges out into a hemisphere, the surface etched with almost-legible letters that spiral around it and converge in the center."
- [ ] "crooked floor": "The scrap metal floor here seems to connect seamlessly to the floors around it, but also looks like it is cocked at a steep angle. It's hard to look at, and harder to balance on." - movement penalty and chance of losing balance
- [ ] "twisted rubble": "The terrain here folds and twists in on itself into a hazardous, sharp-edged tangle of wire and sheet metal. You could try climbing over it, but it looks risky."
- [ ] "twisted barricade": "The terrain here folds and twists in on itself into an impassable tangle of metal sheets and wires, spiralling into themselves."
- [ ] "glowing metal wall": A scrap metal wall with pulsing light coming through the cracks from an unseen source. - add flickering light source field.
- [ ] "glowing metal floor": As above
- [ ] "improbable door": "You can tell this is a door. You're not really sure how you can tell. It just gives off a sort of vague 'doorishness'. It doesn't appear to have hinges, or a handle, and it seems to swing open from the middle."

#### Items related to terrain/furniture
- [ ] "handful of nanosand": "These silvery particles feel just slightly warmer than their surroundings, and when allowed to fall seem to always fall into geometric patterns, with a preference for spirals." - can be mixed with concrete, nanosand concrete hardens into reinforced concrete in construction, saving steps and time. Can be mixed with real sand and used to make reinforced or bulletproof glass with appropriate tools.
- [ ] "bushel of wiregrass": "Somehow, upon harvesting, this metallic gold-and-silver wiregrass seems to have lost its keen edge. You could still fetch a nasty papercut on the leaves if you aren't careful, but it's nowhere near as deadly as when it was still in the ground. Many of the stalks are heavy with seedlike bunches of metal."
- [ ] "wiregrass 'seeds'": "You've threshed the seeds off of a bushel of golden wiregrass, yielding small pellets of what appears to be brass or bronze. It's unlikely they would grow... right?" - note, they do not grow, but could have other uses
- [ ] "wiregrass stalks": "The cleaned and trimmed stalks of wiregrass appear to be pretty boring stalks of some kind of light metal, perhaps steel or aluminum. They still have a visible fibrous growth pattern on them. If they contain organic material they might be usable as a makeshift welding rod..." - (and they are)
- [ ] "disconnected fracterminal": (you can unplug these and reconnect them in your base as an appliance, what does that do? potentially a few different things, hard to say!)
- [ ] "disconnected fabonator": "Now you can just reinstall this fabonator anywhere you want, allowing you to... um..." - can be installed as an appliance, does nothing(?)

### Describe alternatives you have considered.

Open to new ideas.

### Additional context

I will try to code and draw a few of these in the days to come so that some prototype maps can be drawn up.

No files or tests are named. Start by reviewing the related issue 55794 and the existing Exodii base palettes, then identify the relevant terrain, furniture, item, and map-generation systems. Done would require implementing a selected set of Labyrinthine Structure objects and producing prototype maps, but the issue leaves the scope open.

Written by the indexing model from the issue text.