[ready] adds unit test for missing inhand icons. fixes a bunch of missing inhand icons (#70037)

fix: Fixed a bunch of missing inhand icons.
fix: Fixed cables in electrical toolboxes not randomizing their colors.
fix: Fixed the wrong colored icon showing when trying to make cable cuffs out of cables.
fix: The collectable SWAT helmet is now using the proper icon again!
refactor: Pipecleaners and power cables now share a unified color system, so they're once again available in ALL the same colors.
imageadd: Updated the screwdriver belt overlay to represent the newer sprite.
imageadd: Added a bunch of new inhand icons. Special thanks to Twaticus for doing the helmets! <3
fix: Wirecutters now have an icon when inside a belt again!
admin: Added a new omnitool subtype that allows you to spawn all items in a typepath!
fix: Explorer gaskmasks now properly reflect their adjusted state when held.
fix: Fixed balaclavas having the wrong icon when pulled up.
fix: Fixed the base energy sword (admin spawn only) being invisible.
fix: The rainbow energy sword is now a little bit more rainbowy!
fix: Fixed an tk exploit with orange handcuffed shoes.
fix: The traitor outfit in the select equipment panel is now actually functional!

code/modules/mob/living/basic/lavaland/bileworm/bileworm_instrument.dm

@@ -5,7 +5,7 @@
 	icon = 'icons/mob/simple/lavaland/bileworm.dmi'
 	icon_state = "bilehorn"
 	allowed_instrument_ids = "bilehorn"
-	inhand_icon_state = "bilehorn"
+	inhand_icon_state = null
 
 /datum/crafting_recipe/bilehorn
 	name = "Bilehorn"

code/modules/mob/living/basic/lavaland/bileworm/bileworm_loot.dm

@@ -7,7 +7,7 @@
 	singular_name = "bileworm skin piece"
 	icon = 'icons/mob/simple/lavaland/bileworm.dmi'
 	icon_state = "sheet-bileworm"
-	inhand_icon_state = "sheet-bileworm"
+	inhand_icon_state = null
 	merge_type = /obj/item/stack/sheet/animalhide/bileworm
 
 //trophy