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/UserInterface/Controls/FancyWindow.xaml

@@ -1,8 +1,8 @@
 
-<ui:FancyWindow xmlns="https://spacestation14.io"
-                xmlns:ui="clr-namespace:Content.Client.UserInterface"
-                MouseFilter="Stop"
-                MinWidth="200" MinHeight="150">
+<controls:FancyWindow xmlns="https://spacestation14.io"
+                      xmlns:controls="clr-namespace:Content.Client.UserInterface.Controls"
+                      MouseFilter="Stop"
+                      MinWidth="200" MinHeight="150">
     <PanelContainer StyleClasses="AngleRect" />
 
     <BoxContainer Orientation="Vertical">
@@ -18,4 +18,4 @@
         <PanelContainer StyleClasses="LowDivider" />
         <Control Access="Public" Name="ContentsContainer" Margin="0 2" RectClipContent="True" VerticalExpand="true" />
     </BoxContainer>
-</ui:FancyWindow>
+</controls:FancyWindow>

Content.Client/UserInterface/Controls/FancyWindow.xaml.cs

@@ -3,7 +3,7 @@ using Robust.Client.UserInterface.CustomControls;
 using Robust.Client.UserInterface.XAML;
 using Robust.Shared.Maths;
 
-namespace Content.Client.UserInterface
+namespace Content.Client.UserInterface.Controls
 {
     [GenerateTypedNameReferences]
     [Virtual]

Content.Client/UserInterface/Controls/HighDivider.cs

@@ -0,0 +1,14 @@
+using Content.Client.Stylesheets;
+using Robust.Client.UserInterface;
+using Robust.Client.UserInterface.Controls;
+
+namespace Content.Client.UserInterface.Controls
+{
+    public sealed class HighDivider : Control
+    {
+        public HighDivider()
+        {
+            Children.Add(new PanelContainer {StyleClasses = {StyleBase.ClassHighDivider}});
+        }
+    }
+}