Make manual valves work (#6121)

* Make manual valves work

* Change some GasValveSystem lookups

Content.Client/Atmos/Visualizers/GasValveVisualizer.cs

@@ -0,0 +1,18 @@
+using System;
+using Content.Shared.Atmos.Piping;
+using JetBrains.Annotations;
+
+namespace Content.Client.Atmos.Visualizers
+{
+    [UsedImplicitly]
+    public class GasValveVisualizer : EnabledAtmosDeviceVisualizer
+    {
+        protected override object LayerMap => Layers.Enabled;
+        protected override Enum DataKey => FilterVisuals.Enabled;
+
+        enum Layers : byte
+        {
+            Enabled,
+        }
+    }
+}