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.Client/Administration/AdminSystem.Overlay.cs

@@ -0,0 +1,25 @@
+using Robust.Client.UserInterface.Controls;
+
+namespace Content.Client.Administration
+{
+    public partial class AdminSystem
+    {
+        private AdminNameOverlay _adminNameOverlay = default!;
+
+        private void InitializeOverlay()
+        {
+            _adminNameOverlay = new AdminNameOverlay(this, _entityManager, _eyeManager, _resourceCache, _entityLookup);
+        }
+
+        public void AdminOverlayOn(BaseButton.ButtonEventArgs? _ = null)
+        {
+            if (!_overlayManager.HasOverlay<AdminNameOverlay>())
+                _overlayManager.AddOverlay(_adminNameOverlay);
+        }
+
+        public void AdminOverlayOff(BaseButton.ButtonEventArgs? _ = null)
+        {
+            _overlayManager.RemoveOverlay<AdminNameOverlay>();
+        }
+    }
+}