Gas masks give gas immunity

[blackdav123]

Description

Gas masks give complete immunity to standing inside chem gases, even on otherwise naked marines.

Test Merges

#15682: 'Smooth move update' by Lumipharon at commit a1f2eeb30e
#15693: 'Removes the ability to build cades on tadpoles, adds a new mapping helper and flag' by Wisemonster at commit cd0924c97e
#15694: 'Removes minimum pop from Transport Crewmen' by Wisemonster at commit aa5314de1a

Reproduction Steps

1. Put a gas mask of any kind on a human
2. Use defiler gases or shuffle the human into prae neuro (direct hits work but the gas itself doesnt)
3. Human wont get any chems inside them

Screenshots

No response