Being drunk or having a broken arm hurts accuracy with ranged weapons. Also cleans up a fair bit of hand handling to be more readable (#87904)

## About The Pull Request

1. Having a broken arm will affect your accuracy when firing a weapon
with that arm, even potentially causing damage to you if it's a weapon
with recoil. This effect is not applied under the effects of a
painkiller.

2. The sister effect of this (punching someone with a broken arm) now
also has an interact with painkillers (it can no longer block your
attack).

3. Being drunk heavily affects ranged weapon accuracy, unless you're the
bartender

4. A lot of hand handling cleanup, using new macros to make it a lot
more readable at a glance

## Why It's Good For The Game

We have this system for modifying firearm accuracy but we don't really
use it commonly, and I feel like it slots in well with a lot of places

For broken arms, it adds some more depth to the wound system, in the
same way that trying to punch someone with a broken arm causes pain. (I
actually want to expand this to melee weapon accuracy and attacking with
melee weapons in general, but that's for a later time)

For drunkenness, it just adds to the drunk shenanigans. It also slightly
reduces the effectiveness of drinks as combat healing chemicals, such as
quadsec - makes it a bit more of a trade off.

## Changelog

🆑 Melbert
balance: Having a broken arm affects your accuracy with ranged weapons
fired with that arm. Utilizing a painkiller will nullify this effect,
however.
balance: Painkillers will prevent your punches from being cancelled due
to having a broken arm. You'll still take damage, though.
balance: Being drunk now affects your accuracy with ranged weapon. The
bartender is immune to this effect via their skillchip.
code: A lot of code involving left and right hand handling has been
cleaned up, easier to read. Report any oddities, like left and rights
being flipped
/🆑

code/datums/components/basic_inhands.dm

@@ -39,7 +39,7 @@
 	SIGNAL_HANDLER
 	var/list/held_overlays = list()
 	for(var/obj/item/held in holding_mob.held_items)
-		var/is_right = holding_mob.get_held_index_of_item(held) % 2 == 0
+		var/is_right = IS_RIGHT_INDEX(holding_mob.get_held_index_of_item(held))
 		var/icon_file = is_right ? held.righthand_file : held.lefthand_file
 		var/mutable_appearance/held_overlay = held.build_worn_icon(default_layer = HANDS_LAYER, default_icon_file = icon_file, isinhands = TRUE)
 		held_overlay.pixel_y += y_offset

code/datums/components/gunpoint.dm

@@ -194,7 +194,7 @@
 		return
 
 	var/flinch_chance = 50
-	var/gun_hand = (source.get_held_index_of_item(weapon) % 2) ? BODY_ZONE_L_ARM : BODY_ZONE_R_ARM
+	var/gun_hand = IS_LEFT_INDEX(source.get_held_index_of_item(weapon)) ? BODY_ZONE_L_ARM : BODY_ZONE_R_ARM
 
 	if(isbodypart(def_zone))
 		var/obj/item/bodypart/hitting = def_zone

code/datums/components/infective.dm

@@ -115,8 +115,8 @@
 		return
 
 	if(!is_weak)
-		var/appendage_zone = feeder.held_items.Find(source)
-		appendage_zone = appendage_zone == 0 ? BODY_ZONE_CHEST : (appendage_zone % 2 ? BODY_ZONE_R_ARM : BODY_ZONE_L_ARM)
+		var/appendage_zone = feeder.get_held_index_of_item(source)
+		appendage_zone = appendage_zone == 0 ? BODY_ZONE_CHEST : (IS_RIGHT_INDEX(appendage_zone) ? BODY_ZONE_R_ARM : BODY_ZONE_L_ARM)
 		try_infect(feeder, appendage_zone)
 
 	for(var/datum/disease/disease as anything in diseases)

code/datums/components/mutant_hands.dm

@@ -160,11 +160,9 @@
 	if(!base_icon_state)
 		return
 
-	// Even hand indexes are right hands,
-	// Odd hand indexes are left hand
-	// ...But also, we swap it intentionally here,
+	// We swap it intentionally here,
 	// so right icon is shown on the left (Because hands)
-	if(user.get_held_index_of_item(src) % 2 == 1)
+	if(IS_LEFT_INDEX(user.get_held_index_of_item(src)))
 		icon_state = "[base_icon_state]_right"
 	else
 		icon_state = "[base_icon_state]_left"

code/datums/components/supermatter_crystal.dm

@@ -165,10 +165,7 @@
 		var/obj/item/cigarette/cig = item
 		var/clumsy = HAS_TRAIT(user, TRAIT_CLUMSY)
 		if(clumsy)
-			var/which_hand = BODY_ZONE_L_ARM
-			if(!(user.active_hand_index % 2))
-				which_hand = BODY_ZONE_R_ARM
-			var/obj/item/bodypart/dust_arm = user.get_bodypart(which_hand)
+			var/obj/item/bodypart/dust_arm = user.get_active_hand()
 			dust_arm.dismember()
 			user.visible_message(span_danger("The [item] flashes out of existence on contact with \the [atom_source], resonating with a horrible sound..."),\
 				span_danger("Oops! The [item] flashes out of existence on contact with \the [atom_source], taking your arm with it! That was clumsy of you!"))