adds crushed can, jelly doughnut, and shipping container random spawners (#78444)

## About The Pull Request
i got bored so i made some new spawners, mainly for mappers but maybe an
admin will use them too. pics here:

![image](https://github.com/tgstation/tgstation/assets/110322848/2cd121dc-6fa6-46fd-bd9f-4cab72ead9c7)

firstly, this adds crushed can spawners, for if you want a random
crushed can sprite in your map, and don't really care which it is.
if you _do_ care, however - you can set the var/random_icon field on one
of these to 0, in your copy of strongdmm. then just change the icon
state to whatever specific can design you'd like it to be (ie:
"wellcheers")
here you can see a few of them in action

![image](https://github.com/tgstation/tgstation/assets/110322848/9fa3e210-e979-42c7-8f8c-d155ca2fe9bb)

secondly, this adds doughnut, jelly doughnut, and slime jelly doughnut
spawners - pictured below
these use a weighted list based on flavor - more down to earth flavors
are more common, while more interesting and unique flavors like bungo
and blumpkin are a bit rarer.

![image](https://github.com/tgstation/tgstation/assets/110322848/31cf6677-9f4b-40d0-91f0-bcdd59803e74)

thirdly, this adds a shipping container spawner. this one uses a
weighted list so the super obvious syndi corps are rare, less obvious
ones are less rare, and regular corporate ones are common. here you can
see a few.

![image](https://github.com/tgstation/tgstation/assets/110322848/8a8731e7-f6fc-4b91-9680-5b6b93619430)
## Why It's Good For The Game
more flexibility for mappers, more dynamic spawns... what's not to love?
## Changelog
🆑
not player facing
/🆑

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

code/game/objects/structures/containers.dm

@@ -53,6 +53,7 @@
 	name = "\improper Nanotrasen shipping container"
 	desc = "A standard-measure shipping container for bulk transport of goods. This one prominently features Nanotrasen's logo, and so presumably could be carrying anything."
 	icon_state = "nanotrasen"
+
 /obj/structure/shipping_container/nthi
 	name = "\improper Nanotrasen Heavy Industries shipping container"
 	desc = "A standard-measure shipping container for bulk transport of goods. This one is from NTHI: Nanotrasen's mining and refining subdivision."