Move/Rename stuff (#11209)

-     Change namespace, and folder of FancyWindow to Content.Client.UserInterface.Controls
-     Change xaml reference from ui to controls in some places
-     Change ClientAlertsSystem from internal to public
-     Change namespace, and folder of HighDivider to Content.Client.UserInterface.Controls

Content.Client/Hands/ShowHandItemOverlay.cs

@@ -1,3 +1,4 @@
+using Content.Client.Hands.Systems;
 using Content.Shared.CCVar;
 using Robust.Client.GameObjects;
 using Robust.Client.Graphics;