Prevent space from freezing things via gas conduction

[out-of-phaze]

Description of changes

Heat transfer rate from local air to atoms now scales with air pressure.

Why and what will this PR improve

Fixes #4163.

Currently, vacuum freezes things because it's at 2.7K even though there's no gas to transfer heat to. Now, at 0kPa no heat transfer will occur, and at 10kPa it'll equalize ten times as quickly (though maybe it'd be better to cap it at a max of 1x?)

In the future we can add radiation separately, but I would much rather have the issue of hot things not cooling down (since everything that does that presently has it hardcoded separately) than everything becoming ice-cold no matter what. This is gamebreaking, a lack of radiative cooling is relatively small.

Authorship

Me.

[MistakeNot4892]

Would like to revisit this if we get issues where post-fire situations are full of white-hot metal rods or whatever, but in the meantime this seems unlikely to cause serious issues.