The Shovellening: Coroner and Miner Coats can now hold Shovels (#83139)

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## About The Pull Request
The Shovel, Serrated Bone Shovel, and the Entrenching Tooll can now be
worn on the Coroner/Miner Winter Coats, as well as upon the Coroner's
labcoat. Normally, shovels worn on the belt slot are displayed on your
sprite at your back, and allowing them to go on the suit slot initially
mirrored them to the front on side-facing mobs.

I've changed the mirrored sprites for side-facing in the belt_mirror.dmi
in order to _not_ be mirrored, so they display properly on the back. Not
a very elegant way to do it, but this hasn't caused issues with
double-equipping shovels in testing.


![shovel_example](https://github.com/tgstation/tgstation/assets/147954468/f7258466-f4f2-4869-9302-199e76759766)
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## Why It's Good For The Game
Miner Winter Coats should be able to hold shovels as they're mining
tools to begin with, and Coroners should be able to do the same in order
to dig or dig up graves. The Serrated Shovel, as well, is the only
Morbid Bone Saw equivalent in the game as far as I know, so this would
allow Coroners to carry that Morbid equivalent without taking up bag
space. This encourages Coroners to lean further into the flavor of their
role as Morbid or Occultic Medbay personnel.
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## Changelog

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🆑 Jane
qol: Shovels, Serrated Bone Shovels, and Entrenching Tools can now be
hung upon Miner and Coroner Winter Coats, as well as the Coroner's
Labcoat!
image: Mirrored the mirrored sprites to display Shovels in the suit slot
properly.
/🆑

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---------

Co-authored-by: Ghom <42542238+Ghommie@users.noreply.github.com>

code/modules/clothing/suits/labcoat.dm

@@ -106,6 +106,9 @@
 	allowed += list(
 		/obj/item/autopsy_scanner,
 		/obj/item/scythe,
+		/obj/item/shovel,
+		/obj/item/shovel/serrated,
+		/obj/item/trench_tool,
 	)
 
 /obj/item/clothing/suit/toggle/labcoat/science

code/modules/clothing/suits/wintercoats.dm

@@ -384,6 +384,9 @@
 	allowed += list(
 		/obj/item/autopsy_scanner,
 		/obj/item/scythe,
+		/obj/item/shovel,
+		/obj/item/shovel/serrated,
+		/obj/item/trench_tool,
 	)
 
 /obj/item/clothing/head/hooded/winterhood/medical/coroner
@@ -629,6 +632,8 @@
 		/obj/item/storage/bag/ore,
 		/obj/item/t_scanner/adv_mining_scanner,
 		/obj/item/tank/internals,
+		/obj/item/shovel,
+		/obj/item/trench_tool,
 	)
 	armor_type = /datum/armor/wintercoat_miner
 	hoodtype = /obj/item/clothing/head/hooded/winterhood/miner