[ICEMETA] [GAX] Changes stairs (the ones that actually let you travel z-levels) render plane, fixes some mapping bugs

[AMyriad]

Document the changes in your pull request

• I'm tired of not being able to put ramp shadows on these things since they're structures, so I've moved them down to the floor plane (layer 2).

• And because we often use stairs (actually tiles, but they make people think they're stairs) that look like this:

and not this: (ugly) (how structure stairs look (not floor tile))

we now have stairs (structure) that look like the above!

And tiny map fixes because

• IceMeta stairs in mining now use above ^ better looking stairs
• Added some ramp shadows to Gax stairs
• Fixed an access-related bug I noticed while doing the maptainer test a few months ago lol

Why is this good for the game?

Lets me do my job better and map faster!!!

Testing

Will do

Changelog

:cl: experimental: Actual stairs (currently only exist on IceMeta) are now visually rendered lower than some objects, you make report if see any issue yes? mapping: The stairs found in mining on IceMeta now look a bit nicer mapping: The stairs in the garden on NVS Gax now have some nice shading mapping: The botanist's windoor between hydroponics and the kitchen on NVS Gax can no longer be opened with RD access (lol, lmao even) /:cl: