[MIRROR] Cake baking autotest (#28756)

* Cake baking autotest (#84795)

## About The Pull Request

I want to get back to the food stuff, and adding a few auto tests to
avoid regressions.

The test makes a dummy human bake a cake from the base ingredients,
confirming that the reagent purities are correct and that the cake slice
gives a food buff in the end.

## Why It's Good For The Game

Avoiding bugs.

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

* Cake baking autotest

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

code/modules/unit_tests/_unit_tests.dm

@@ -96,6 +96,7 @@
 #include "armor_verification.dm"
 #include "atmospherics_sanity.dm"
 #include "autowiki.dm"
+#include "bake_a_cake.dm"
 #include "barsigns.dm"
 #include "baseturfs.dm"
 #include "bespoke_id.dm"