Move GasMixture to shared (#27480)

* Moved GasMixture to shared

* Temp Fix for sandbox violation, idk why Array.Resize isn't working properly. It's already sandboxed.

* The most powerful webedit in history

Content.Server/Power/Generator/GeneratorExhaustGasSystem.cs

@@ -1,5 +1,6 @@
 using Content.Server.Atmos;
 using Content.Server.Atmos.EntitySystems;
+using Content.Shared.Atmos;
 using Content.Shared.Power.Generator;
 
 namespace Content.Server.Power.Generator;