Add CVar to disable pow3r parallel processing (#28488)

* Add CVar to disable pow3r parallel processing

* Cache CVar value

* Fix pointyhat

* Move all CVar-ing to Content.Server

Content.Server/Power/EntitySystems/PowerNetSystem.cs

@@ -3,9 +3,11 @@ using Content.Server.NodeContainer.EntitySystems;
 using Content.Server.Power.Components;
 using Content.Server.Power.NodeGroups;
 using Content.Server.Power.Pow3r;
+using Content.Shared.CCVar;
 using Content.Shared.Power;
 using JetBrains.Annotations;
 using Robust.Server.GameObjects;
+using Robust.Shared.Configuration;
 using Robust.Shared.Threading;
 
 namespace Content.Server.Power.EntitySystems
@@ -18,6 +20,7 @@ namespace Content.Server.Power.EntitySystems
     {
         [Dependency] private readonly AppearanceSystem _appearance = default!;
         [Dependency] private readonly PowerNetConnectorSystem _powerNetConnector = default!;
+        [Dependency] private readonly IConfigurationManager _cfg = default!;
         [Dependency] private readonly IParallelManager _parMan = default!;
         [Dependency] private readonly PowerReceiverSystem _powerReceiver = default!;
 
@@ -25,13 +28,14 @@ namespace Content.Server.Power.EntitySystems
         private readonly HashSet<PowerNet> _powerNetReconnectQueue = new();
         private readonly HashSet<ApcNet> _apcNetReconnectQueue = new();
 
-        private readonly BatteryRampPegSolver _solver = new();
+        private BatteryRampPegSolver _solver = new();
 
         public override void Initialize()
         {
             base.Initialize();
 
             UpdatesAfter.Add(typeof(NodeGroupSystem));
+            _solver = new(_cfg.GetCVar(CCVars.DebugPow3rDisableParallel));
 
             SubscribeLocalEvent<ApcPowerReceiverComponent, ComponentInit>(ApcPowerReceiverInit);
             SubscribeLocalEvent<ApcPowerReceiverComponent, ComponentShutdown>(ApcPowerReceiverShutdown);
@@ -53,6 +57,13 @@ namespace Content.Server.Power.EntitySystems
             SubscribeLocalEvent<PowerSupplierComponent, ComponentShutdown>(PowerSupplierShutdown);
             SubscribeLocalEvent<PowerSupplierComponent, EntityPausedEvent>(PowerSupplierPaused);
             SubscribeLocalEvent<PowerSupplierComponent, EntityUnpausedEvent>(PowerSupplierUnpaused);
+
+            Subs.CVar(_cfg, CCVars.DebugPow3rDisableParallel, DebugPow3rDisableParallelChanged);
+        }
+
+        private void DebugPow3rDisableParallelChanged(bool val)
+        {
+            _solver = new(val);
         }
 
         private void ApcPowerReceiverInit(EntityUid uid, ApcPowerReceiverComponent component, ComponentInit args)