Fireaxe cabinet construction fixes

Created by: Exxion

I love the mountable frames code

• Building a fireaxe cabinet with plasteel gives you a fireaxe cabinet frame rather than just builds a cabinet where you're standing.
  • Fireaxe cabinet frame has a sprite intended to be a placeholder, though I guess it could stay. It looks just like an empty fireaxe cabinet that's half open.
  • This can be placed on a wall just like any other frame.
  • Fireaxe cabinets placed with a frame start empty, open, and unlocked.
    • They also, like all mounted frames that appear "inside" a wall (except air alarms), correctly prevent other frames from being placed on the same side of the same wall as themselves, which was substantially harder to get working than it should have been for reasons I don't entirely understand.
• Fireaxe cabinets now render just above the turf layer because their sprites are huge and tended to cover up the sprites of other objects mounted on other sides of the same wall.

Issues I noticed while testing this but did not fix:

• Air alarms (possibly other things, but I only noticed air alarms failing to do this) do not prevent you from placing other frames on the same side of the same wall as themselves. Not totally sure why.
• Fireaxe cabinets are always placed in the center of the wall they are placed on, while everything else is offset somewhat depending on the side. This means that two fireaxe cabinets placed on different sides of the same wall will cover each other up and each will only be accessible from certain angles because BYOND has trouble deciding which should be rendered on top. Fixing this for constructed cabinets would be easy, and I can do it in this PR if asked, but fixing it in general would require map changes, which I don't want to do because of possible conflicts.
• There is, as far as I can tell, no legitimate access requirement for the fireaxe cabinet other than the AI. Assistants and captains alike need to either break it or multitool it.

Fixes #4278 (closed)