Better Gas masks - Model concentration better, and make gas mask cartiges last longer

[MorvarchPrincess]

Summary

Balance "Gas mask cartriges last quite a bit longer, and lower concentration gas takes less charges"

Purpose of change

Per issue #68554, our gas masks last a really short amount of time. I considered just about tripling the gas mask charge costs to bring it in line with estimates mentioned in the issue, but decided it would be better to have a concentration calculation in the charge buildup.

Describe the solution

My aim is to have an additional entry for gasses that is "concentration" that acts as a multiplier on charges spent, so thick toxic gas burns through your charges quicker than thin gas. I'll then go adjust numbers for gasses so that thick toxic gas means your gas mask will last about 20 minutes, and less problematic substances (read normal smoke) arn't as bad.

I also switched how the gas_absorption_factor works, it's now no longer what percent of a charge it uses per tick, its now how long a full 100 charge filter lasts in a concentration 1 gas.

Finally I also added another little message to the player when their gas mask charges go under 10. IRL a gas mask gets harder to breathe in as the filter clogs up, so it made sense for players to get a warning as they are running out.

Describe alternatives you've considered

I could just not add concentration, which would just require adjusting the gas absorption numbers, but it would still leave light gasses to unrealistically burn through charges.

I also considered basing the multiplier on intensity, but that doesn't work great as that number is primarily used for the amount of effect, and as such the numbers don't line up (toxic gas and thick toxic gas have the same number at 4) and could get modified and cause unintentional changes to gas mask charges.

Finally, I could have left gas absorption values the same, but it ended up with some very messy calculations so I decided it was better to change how the system works to be more based on how we measure gas mask lifetime in real life.

Testing

Tested both manually and via walking through code.

I booted up the game and spawned a gas vent in a small building. then waited till the room filled up. I then both watched the calculation via stepping through code, and confirmed it was taking the appropriate amount of charges off by waiting in the cloud with a mask on.

Additional context