[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/game/objects/structures/tables_racks.dm

@@ -841,6 +841,7 @@
 	desc = "Parts of a rack."
 	icon = 'icons/obj/weapons/items_and_weapons.dmi'
 	icon_state = "rack_parts"
+	inhand_icon_state = "rack_parts"
 	flags_1 = CONDUCT_1
 	custom_materials = list(/datum/material/iron=2000)
 	var/building = FALSE

code/game/objects/structures/watercloset.dm

@@ -248,6 +248,8 @@ MAPPING_DIRECTIONAL_HELPERS(/obj/structure/urinal, 32)
 	icon = 'icons/obj/watercloset.dmi'
 	icon_state = "rubberducky"
 	inhand_icon_state = "rubberducky"
+	lefthand_file = 'icons/mob/inhands/items_lefthand.dmi'
+	righthand_file = 'icons/mob/inhands/items_righthand.dmi'
 	worn_icon_state = "duck"
 
 /obj/structure/sink