BIO_IMMUNE is missing a JSON flag definition and errors if defined in the game

[RoyalFox2140]

Describe the bug

Whenever @scarf005 did #3225 we needed a flag for monsters to be immune to biological damage it wasn't realized by any involved parties that BIO_IMMUNE exists in character.cpp but doesn't have a json flag definition so it errors out on usage. This seems like a minor fix but it's also fairly confusing that character and monster has separate flag names for the same effect. I think ideally we would migrate all damage immunity flags to be named the same, but for now we need a flag definition for BIO_IMMUNE.

I'm leaving a note here that refactoring all of the immunity flags in character.cpp is most ideal to avoid confusion about using the wrong flag.

Steps To Reproduce

1. Check character.cpp for "BIO_IMMUNE"
2. Check monster.cpp for "BIOPROOF"
3. Check flags.json for "BIO_IMMUNE"

Screenshots

Versions and configuration

OS: Windows
OS Version: 10.0.19045.3448 (22H2)
Game Version: ed1f287 [64-bit]
Graphics Version: Tiles
LAPI Version: 2
Game Language: English [en_US]
Mods loaded: [
Bright Nights [bn],
Craftable Gun Pack [craftgp],
Alternative Map Key [alt_map_key],
Fuji's Military Profession Pack [fuji_mpp],
Craftable Bullet Casings [CasingCrafting],
MST Extra [MST_Extra],
Tankmod: Revived [Tankmod_Revived],
Essence 2200 BN [Essence2200_BN],
Essence 2200 Tweaks [FoxTweaks],
Nonperishable Overhaul [Nonperishable_Overhaul],
No Addictions [No_Addictions],
Limit Fungal Growth [limit_fungal_growth],
Disable NPC Needs [no_npc_food],
Simplified Nutrition [novitamins],
OMT Resources [omt_resources],
Flowing Water [flowing_water],
No Filthy Clothing [no_filthy_clothing],
Cataclysm++ [Cata++]
]

Additional context

No response

[chaosvolt]

Weird, EFFECT_BIO_IMMUNE is properly defined for immunity from effects, just not BIO_IMMUNE for immunity from armor.