Add a unit test to check that maploaded simple/basic mobs are in an environment they can survive in. (#82180)

## About The Pull Request
I've recently noticed that the maploaded penguins from the snowdin away
mission were dying from unsafe atmos/temperature. This sparked the idea
of making a (focus only) unit test that would prevent this sort of
issues from happening.

This PR also implements the usage of the `atmos_requirements` and
`body_temp_sensitive` elements for simple animals too, cutting down the
copypaste.

## Why It's Good For The Game
More unit tests to make sure things are done correctly.

## Changelog

🆑
fix: Made sure that mapped critters (i.e. penguins on the snow cabin
away mission) can survive in the environment they're spawned in.
/🆑

code/modules/mob/living/basic/pets/dog/dog_subtypes.dm

@@ -38,6 +38,13 @@
 	collar_icon_state = "bullterrier"
 	held_state = "bullterrier"
 
+/mob/living/basic/pet/dog/bullterrier/lavaland_party
+	name = "Saint Nick's Helpful Associate"
+	desc = "Undergraduate in 'Being a Good Boy'."
+	habitable_atmos = null
+	gold_core_spawnable = NO_SPAWN
+	unique_pet = TRUE
+
 /mob/living/basic/pet/dog/breaddog //Most of the code originates from Cak
 	name = "Kobun"
 	real_name = "Kobun"