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/unit_tests/focus_only_tests.dm

@@ -44,3 +44,6 @@
 
 /// Checks that the contents of the fish_counts list are also present in fish_table
 /datum/unit_test/focus_only/fish_sources_tables
+
+/// Checks that maploaded mobs with either the `atmos_requirements` or `body_temp_sensitive`
+/datum/unit_test/focus_only/atmos_and_temp_requirements