refactors adminmenu a timid amount (#5095)

Co-authored-by: Paul <ritter.paul1+git@googlemail.com>
Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Shared/Administration/Events/FullPlayerListEvent.cs

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+using System;
+using System.Collections.Generic;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Administration.Events
+{
+    [Serializable, NetSerializable]
+    public class FullPlayerListEvent : EntityEventArgs
+    {
+        public List<PlayerInfo> PlayersInfo = new();
+    }
+}

Content.Shared/Administration/Events/PlayerInfoChangedEvent.cs

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+using System;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Administration.Events
+{
+    [NetSerializable, Serializable]
+    public class PlayerInfoChangedEvent : EntityEventArgs
+    {
+        public PlayerInfo? PlayerInfo;
+    }
+}

Content.Shared/Administration/Events/PlayerInfoRemovalMessage.cs

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+using System;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Network;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Administration.Events
+{
+    [NetSerializable, Serializable]
+    public class PlayerInfoRemovalMessage : EntityEventArgs
+    {
+        public NetUserId NetUserId;
+    }
+}