[s] Lowers xenomorph acid damage on living mobs

[DGamerL]

What Does This PR Do

Title. Xenomorph acid now does less damage to living mobs.
In return, any acid on the chest (As far as I know, only xenomorphs and probably acid foam/acid smoke can actually touch this) has doubled strength and is applied twice. This means that the maximum acid damage is doubled, and it will reach the maximum damage faster.
Naked humans take 120 burn damage and 60 brute damage from this acid.
Humans with no headgear take 40 burn damage and 20 brute damage.
Fixes #12901

Why It's Good For The Game

Fixes a bug and makes coming into the melee range of xenos slightly more interesting and fair.
Some other testing:

• Skrell in security officer outfit: jumpsuit & protective vest melted in about 25 seconds, helmet and others in about 30 seconds
• Skrell in HOS outfit: same numbers for the helmet and others, armored jacket didn't seem to melt due to high acid armor
• Any MODsuit seems to be immune to this acidmelting of xenos

Testing

See the section in Why it's good for the game

Changelog

🆑
tweak: Acid melts (jump)suits twice as fast now
tweak: xenomorph human acid damage has been reduced
/:cl: