Limbify/flagify field immunity

[Venera3]

Summary

Features "Field immunity changes"

Purpose of change

Fixes #60442 and prepares field immunity for nonstandard limbs.

Describe the solution

Field immunity changes:

• Instead of trait IDs character flags are checked, meaning effects/bionics/bodyparts now all can allow you to ignore certain fields (Potion of Acid Resistance, anyone?)
• Instead of bodypart string IDs the environmental protection check evaluates all bodyparts of a given limb type, any one uncovered limb will render you susceptible to the field
• Added checking for worn item flags worn on a given limb type

Misc changes:

• The searchlight's dazzling explosion got a lowered field chance but a random AOE
• Changed all traits immunities to flags, and added the flags to the relevant traits

Describe alternatives you've considered

Just add a flashbang spell effect to the death function, but I was in an overengineering mood.

Testing

Added the flash protection requirement on the sensor bodypart type to dazzling fields, got blinded without a welding mask but kept my sight with it. Changed the bodypart type to arm and got blinded even with a mask.
Gastropod foot still confers immunity to sludge fields.
Activated gas masks confer immunity to toxic clouds.

Additional context

There's a lot of unhardcoding to do in this space, and the field effect definitions still key off of bodypart IDs, but that's a PR for another time.