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/farm_animals/bee/_bee.dm

@@ -39,7 +39,7 @@
 	can_be_held = TRUE
 	held_w_class = WEIGHT_CLASS_TINY
 	environment_smash  = ENVIRONMENT_SMASH_NONE
-	habitable_atmos = list("min_oxy" = 0, "max_oxy" = 0, "min_plas" = 0, "max_plas" = 0, "min_co2" = 0, "max_co2" = 0, "min_n2" = 0, "max_n2" = 0)
+	habitable_atmos = null
 	basic_mob_flags = DEL_ON_DEATH
 	ai_controller = /datum/ai_controller/basic_controller/bee
 	///the reagent the bee has

code/modules/mob/living/basic/farm_animals/deer.dm

@@ -49,5 +49,5 @@
 
 /// Cold resistent and doesn't need to breathe
 /mob/living/basic/deer/ice
-	habitable_atmos = list("min_oxy" = 0, "max_oxy" = 0, "min_plas" = 0, "max_plas" = 0, "min_co2" = 0, "max_co2" = 0, "min_n2" = 0, "max_n2" = 0)
+	habitable_atmos = null
 	minimum_survivable_temperature = 0

code/modules/mob/living/basic/farm_animals/pony.dm

@@ -129,7 +129,7 @@
 	faction = list(ROLE_SYNDICATE)
 	ponycolors = list("#5d566f", COLOR_RED)
 	pressure_resistance = 200
-	habitable_atmos = list("min_oxy" = 0, "max_oxy" = 0, "min_plas" = 0, "max_plas" = 0, "min_co2" = 0, "max_co2" = 0, "min_n2" = 0, "max_n2" = 0)
+	habitable_atmos = null
 	minimum_survivable_temperature = 0
 	maximum_survivable_temperature = 1500
 	unique_tamer = TRUE