Refactors stunnable to be ECS. (#4819)

Also cleans up StandingStatesystem.

Content.Server/Stunnable/StunSystem.cs

@@ -0,0 +1,52 @@
+using System;
+using Content.Server.Act;
+using Content.Server.Popups;
+using Content.Shared.Audio;
+using Content.Shared.Popups;
+using Content.Shared.Stunnable;
+using Robust.Shared.Audio;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Localization;
+using Robust.Shared.Player;
+using Robust.Shared.Random;
+
+namespace Content.Server.Stunnable
+{
+    public sealed class StunSystem : SharedStunSystem
+    {
+        [Dependency] private readonly IRobustRandom _random = default!;
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeLocalEvent<StunnableComponent, DisarmedActEvent>(OnDisarmed);
+        }
+
+        private void OnDisarmed(EntityUid uid, StunnableComponent stunnable, DisarmedActEvent args)
+        {
+            if (args.Handled || !_random.Prob(args.PushProbability))
+                return;
+
+            Paralyze(uid, TimeSpan.FromSeconds(4f), stunnable);
+
+            var source = args.Source;
+            var target = args.Target;
+
+            if (source != null)
+            {
+                SoundSystem.Play(Filter.Pvs(source), stunnable.StunAttemptSound.GetSound(), source, AudioHelpers.WithVariation(0.025f));
+
+                if (target != null)
+                {
+                    // TODO: Use PopupSystem
+                    source.PopupMessageOtherClients(Loc.GetString("stunnable-component-disarm-success-others", ("source", source.Name), ("target", target.Name)));
+                    source.PopupMessageCursor(Loc.GetString("stunnable-component-disarm-success", ("target", target.Name)));
+                }
+            }
+
+            args.Handled = true;
+        }
+    }
+}