Convert StomachBehavior to a component/system + rejig body namespaces (#5249)

* Convert StomachBehavior to a component/system + rejig body namespaces

* test

* slightly more namespace changes

* remove

* Hello?????

* fuck you github test runner

* reviews

* oobsy!

Content.Client/Body/Components/MechanismComponent.cs

@@ -1,4 +1,4 @@
-using Content.Shared.Body.Mechanism;
+using Content.Shared.Body.Components;
 using Robust.Shared.GameObjects;
 
 namespace Content.Client.Body.Components