Make arm/leg components of armor sets consistent with rest of set

[chaosvolt]

Summary

SUMMARY: Bugfixes "Fix arm and leg guards that are part of an armor set having wildly different properties"

Purpose of change

I noticed while fumbling to get leather armor produced that leather arm guards, intended to be worn with leather body armor, and being used together to craft the plated and boiled armor sets, didn't behave the same as leather body armor. It was on the strapped layer instead of normal, and wasn't variable in size.

Describe the solution

1. Set leather arm guards to have VARSIZE, increased encumbrance to 20, and removed STRAPPED flag. Now consistent with leather body armor.
2. Removed STRAPPED flag from chitin and acidchitin arm guards, to be consistent with the body armor item.
3. Replaced STRAPPED with OUTER for plate arm and leg guards, to be consistent with cuirass and with assembled plate armor.

Describe alternatives you've considered

1. Removing BLOCK_WHILE_WORN as well, seems acceptable to have it on. For leather arm guards it's a trade off between upgrading your armor vs. retaining the freedom to block with the arm guards, and chitin arm guards don't have any upgraded merged sets where it'd lose the flag. Steel arm guards losing the BLOCK_WHILE_WORN on being crafted into plate armor, with no advantage to make up for it, is the only real oddity resulting from that.
2. Could update the bone armor too but could also save it for any future revival of it from the depths of obsolescence.
3. Briefly pondered applying similar updates to vambraces but they aren't part of a set, meaning it's reasonable for them to be a standalone arm guard item.

Testing

Ported JSON changes over to check for syntax errors, ran affected files through linter.

Additional context

[chaosvolt]

Looking further at this, there are some additional inconsistencies that could be looked at:

1. Every piece of chitinous armor has MASSIVE protection values, superior to iron-tier armor...except chitin arm guards. I suspect that the arm guards have what's supposed to be the desired value, as it gives you cut protection comparable to iron armors but bash protection not much better than leather, giving it an interesting niche.
2. Acid chitin armor is in the same boat but about a layer or two worth of protection higher. Same guess applies, going with the 12/16 value the arm guards use would put it at a niche where the bash resist is iron-tier while the cut resist is comparable to plate armor, whereas the other value used is almost entirely superior to plate armor.
3. Leather armor is just a complete mess. Leather body armor is 8/8, leather gauntlets and helmet are 6/6, leather armor boots are 10/10. My guess is 8/8 is the intended value, but nerfing leather armor boots is going to be problematic because standard boots have had their armor value thrown COMPLETELY out of whack by the inclusion of rubber as a secondary material, making them 11/5.

Point three, as it pertains to leather helmets, could also be related to #692. Perhaps this warrants a "part two" PR following up on this that addresses weird inconsistencies in armor protection.