[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/instruments/piano_synth.dm

@@ -55,7 +55,7 @@
 	name = "\improper Nanotrasen space pods"
 	desc = "Flex your money, AND ignore what everyone else says, all at once!"
 	icon_state = "spacepods"
-	inhand_icon_state = "spacepods"
+	inhand_icon_state = null
 	slot_flags = ITEM_SLOT_EARS
 	strip_delay = 100 //air pods don't fall out
 	instrument_range = 0 //you're paying for quality here