Add toxic waste map extra

[NetSysFire]

Summary

Content "Add toxic waste map extra"

Purpose of change

Take 2 of #55211. This adds an illegal toxic waste dump where some random company dumped their trash, which includes chemicals. Rarely however, this company might be XEDRA...

Describe the solution

The map extra is basically a pool of sewage with normal or trashy rubble ontop with barrels containing mostly vile stuff scattered. There is an okay chance to get a small amount of some chemicals from the barrels. There is also a big variety of chemical spills, which are basically cosmetic only.

Furthermore, there are three "optional" features which the map extra may feature depending on how the RNG feels:

• Radioactive waste (20% chance), to make it fairer and less surprising to the player it will have a broken fence around it and plutonium slurry.
• Toxic gas vents (90% chance to have at least one of them).
• Mutant corpses (10% chance to encounter at least one), lore-stuff: lab staff dumped them there and may also conveniently forget a note with vague clues where to find labs.

Describe alternatives you've considered

I am open to changing the chances of some stuff. I am also not 100% sure about the chemicals because I am a noob when it comes to that.

I also thought of adding empty and/or damaged atomic batteries and stuff like atomic lamps to the radioactive part.

Testing

Loads correctly, manually explored the world until I found a natural spawn.

Additional context

I might subject the non-illegal toxic waste dump to some love, too. So it is only radioactive when plutonium and stuff is being spawned.
Also, I think liquids does not work with item groups which is a shame really or copy-pasting the liquids into the toxic gas vent would not be necessary, if setting fields would not erase spilled liquids which is a bug I still have to report.

[NetSysFire]

I rebased and yet this damn required test is still failing. Why? I do not see anything related to my PR in the test output, so I have the feeling it may just be one of those random failures again

[NetSysFire]

(╯°□°)╯︵ ┻━┻

The reason the test failed was because the survivor note in the same file, which I have not touched, had a "non-sensical item density" and I did a copy-from from it. Super annoying, I had to search for a fix for something I have not touched.

[NetSysFire]

I know I am being (literally, heh) pushy, but just a FYI that this is ready to merge unless someone objects due to balance reasons.