Webbing (and drop pouches) resprite (#21864)

It always bothered me how the webbings (is that a proper plural form for
them?) poked out from under suit items. But then I remembered that I am
a spriter (allegedly) and can change that, so I did. Hello.

From the changelog:
> - imageadd: "Resprited engineering, medical and security webbings
(which are now thinner to not poke out from under suit clothing) and
drop pouches."
> - imageadd: "Added a proper colorable sprite for the colorable drop
pouches."

Images, as always, in the details below.
Old (current) sprites on the top, new on the bottom unless stated
otherwise.
<details>
<summary> Webbings: </summary>
<img width="2304" height="1536" alt="webbings"
src="https://github.com/user-attachments/assets/03942dff-2deb-4071-992d-f42531d753cb"
/>

</details>

<details>
<summary> Drop pouches: </summary>
<img width="2304" height="1536" alt="drop"
src="https://github.com/user-attachments/assets/8ab8f5f7-2f29-4cc7-babb-e845b9ee1d44"
/>

</details>

As far as attributions go, I referenced the medical webbing from
Shiptest, and modified it for for engineering, security and medical. I
do not know which PR in particular that webbing was added added in, but
I will link the PR which I _believe_ did it:
https://github.com/shiptest-ss13/Shiptest/pull/2748

code/modules/clothing/under/accessories/storage.dm

@@ -178,6 +178,7 @@
 
 /obj/item/clothing/accessory/storage/pouches/colour
 	icon_state = "thigh_colour"
+	item_state = "thigh_colour"
 
 /obj/item/clothing/accessory/storage/knifeharness
 	name = "decorated harness"