mech nitrogen filtering 2 (#19868)

* target oxygen logic

* filter out nitrogen when low on oxygen

* vvrw and datafield for everything

* :trollface:

* bruh does work

* tagless chicken

* move into atmos, make it not depend on mech

* update mech prototype

---------

Co-authored-by: deltanedas <@deltanedas:kde.org>

Content.Server/Mech/Components/MechAirComponent.cs

@@ -6,7 +6,8 @@ namespace Content.Server.Mech.Components;
 public sealed partial class MechAirComponent : Component
 {
     //TODO: this doesn't support a tank implant for mechs or anything like that
-    [ViewVariables(VVAccess.ReadWrite)]
+    [DataField, ViewVariables(VVAccess.ReadWrite)]
     public GasMixture Air = new (GasMixVolume);
+
     public const float GasMixVolume = 70f;
 }