[REFACTOR] Consolidates SLOT_FLAG and SLOT_HUD into one ITEM_SLOT flag (#26743)

* IT WORKS UP UNTIL THIS POINT

* Consolidates SLOT_FLAG and SLOT_HUD into one

* Remove cover_both_ears

* SLOT_HUD to ITEM_SLOT

* Remove clothing_trait changes for the time being

* Remove accidental copy-paste

* Re-add no-slip var

* More failure to copy-paste correctly

* Leftover flag

* Combine left and right slot flags where possible

* UNGOOF MY DEFINES, PHAND IS NOT A THING

* Minor spacing changes

* Some more fixes from merge

* Seperates ITEM SLOT AMOUNT into two defines

* ON SECOND THOUGHT LETS NOT DO THAT.

* Addresses Contra's review

* Thank you GREP

* Rename ITEM_SLOT_FEET to ITEM_SLOT_SHOES

* Added a comment to the bitmasks in clothing defines

* Rename ITEM_SLOT_TIE to ITEM_SLOT_ACCESSORY

* These are for a seperate PR.

* Magboot fixes

* Requested changes

* Re-add accidental removal

* Wrong flags

* Update code/__DEFINES/clothing_defines.dm

Co-authored-by: Contrabang <91113370+Contrabang@users.noreply.github.com>
Signed-off-by: Chap <erwin@lombok.demon.nl>

* Requested changes

* Merge fixes

* Fix double headset

* Fixes multiple accessories

---------

Signed-off-by: Chap <erwin@lombok.demon.nl>
Co-authored-by: Adrer <adrermail@gmail.com>
Co-authored-by: Contrabang <91113370+Contrabang@users.noreply.github.com>

code/modules/instruments/objs/items/headphones.dm

@@ -56,7 +56,7 @@
 	icon_state = item_state = "headphones[on]"
 
 /obj/item/clothing/ears/headphones/item_action_slot_check(slot)
-	if(slot == SLOT_HUD_LEFT_EAR || slot == SLOT_HUD_RIGHT_EAR)
+	if(slot & ITEM_SLOT_BOTH_EARS)
 		return TRUE
 
 /**