feat(balance): update capacity of power armor holsters

[chaosvolt]

Purpose of change

Updates some items I overlooked back when I updated holster sizes in #3159, plus expand on one item's role.

Describe the solution

1. Per Scarf's suggestion, increased max volume of back holster from 9 liters to 10 liters, matching that of power armor back holster.
2. Increased maximum volume of power armor holster from 800 ml to 1 liter and minimum volume from 100 ml to 250 ml, matching standard holster.
3. Altered the power armor chest rig a bit, renaming it to "power armor magazine carrier" to distinguish it from from the carry stats of the standard chest rig. Reduced its max mags down to only 2, but bumped its max volume to 1500 ml and allowed it to hold items with the MAG_BULKY flag. This gives it the ability to stash spare heavy batteries, like what a UPS loads.

Describe alternatives you've considered

1. Allowing the mag pouches to also hold ammo belts via adding a flag to it. 5.56 and 7.62 have a pretty massive volume when maxed out at 500 rounds, and even if toned down to 200 that'd require the mag carrier's capacity to be boosted a bit higher, while it'd hold a 200-round 5.56mm belt a 200-round 7.62mm belt is still just a hair over 2.5 liters.
2. Allowing more mag carrier items to hold MAG_BULKY items.

Testing

Checked affected file for syntax and lint errors.

Additional context

Checklist

[scarf005]

i think increasing volume of both back holster to 10L might be a bit better.

[chaosvolt]

Sure, will do. :>

[scarf005]

I think it'll be OK to allow three mags tho