[IDB IGNORE] Refactor modules/clothing/under to new rendering system (#7177)

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## About The Pull Request
Refactors clothing/under to use the new rendering system for both icons
and flags and does some general rearranging and cleanup of the code
files.
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## Why It's Good For The Game
One single consistent system is good. This also fixes a lot of missing
rolldown, rolled sleeves, and maybe some species specific sprites.
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## Changelog
- Moves clothing/under/accessories to clothing/legacy_accessories
- Reformats under into under/casual, /costumes, /formal, /workwear
folders.
- Changes all /obj/item/clothing/under to use the new clothing render
system
- Annihilates uniform.dmi into a thousand pieces
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🆑 _Shadowcat_
refactor: refactors under clothing to new render system
/🆑

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---------

Co-authored-by: silicons <2003111+silicons@users.noreply.github.com>

code/game/objects/structures/crates_lockers/closets/secure/security.dm

@@ -405,7 +405,6 @@ GLOBAL_LIST_BOILERPLATE(all_brig_closets, /obj/structure/closet/secure_closet/br
 		/obj/item/flashlight/maglight,
 		/obj/item/clothing/head/soft/nanotrasen,
 		/obj/item/clothing/head/beret/nanotrasen,
-		/obj/item/clothing/under/nanotrasen/security,
 		/obj/item/clothing/gloves/black,
 		/obj/item/clothing/shoes/boots/jackboots,
 		/obj/item/clothing/shoes/boots/jackboots/toeless)
@@ -458,8 +457,7 @@ GLOBAL_LIST_BOILERPLATE(all_brig_closets, /obj/structure/closet/secure_closet/br
 		/obj/item/flashlight/maglight,
 		/obj/item/clothing/gloves/black,
 		/obj/item/clothing/shoes/boots/jackboots,
-		/obj/item/clothing/shoes/boots/jackboots/toeless,
-		/obj/item/clothing/under/nanotrasen/security/commander)
+		/obj/item/clothing/shoes/boots/jackboots/toeless)
 
 /obj/structure/closet/secure_closet/nanotrasen_commander/Initialize(mapload)
 	if(prob(25))
@@ -479,7 +477,6 @@ GLOBAL_LIST_BOILERPLATE(all_brig_closets, /obj/structure/closet/secure_closet/br
 
 	starts_with = list(
 		/obj/item/clothing/suit/storage/vest/warden,
-		/obj/item/clothing/under/nanotrasen/security/warden,
 		/obj/item/clothing/suit/storage/vest/wardencoat/alt,
 		/obj/item/clothing/head/helmet/warden,
 		/obj/item/cartridge/security,