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/Launcher/LauncherConnectingGui.xaml

@@ -2,7 +2,7 @@
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:gfx="clr-namespace:Robust.Client.Graphics;assembly=Robust.Client"
          xmlns:parallax="clr-namespace:Content.Client.Parallax"
-         xmlns:ui="clr-namespace:Content.Client.HUD.UI">
+         xmlns:controls="clr-namespace:Content.Client.UserInterface.Controls">
     <parallax:ParallaxControl />
     <Control HorizontalAlignment="Center" VerticalAlignment="Center">
         <PanelContainer StyleClasses="AngleRect" />
@@ -13,7 +13,7 @@
                 <Button Name="ExitButton" Text="{Loc 'connecting-exit'}"
                         HorizontalAlignment="Right" HorizontalExpand="True" />
             </BoxContainer>
-            <ui:HighDivider />
+            <controls:HighDivider />
             <BoxContainer Orientation="Vertical" VerticalExpand="True" Margin="4 4 4 0">
                 <Control VerticalExpand="True" Margin="0 0 0 8">
                     <BoxContainer Orientation="Vertical" Name="ConnectingStatus">