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/Cargo/UI/CargoConsoleMenu.xaml

@@ -1,6 +1,6 @@
-<userInterface:FancyWindow xmlns="https://spacestation14.io"
+<controls:FancyWindow xmlns="https://spacestation14.io"
                            xmlns:gfx="clr-namespace:Robust.Client.Graphics;assembly=Robust.Client"
-                           xmlns:userInterface="clr-namespace:Content.Client.UserInterface"
+                           xmlns:controls="clr-namespace:Content.Client.UserInterface.Controls"
                            SetSize="600 600"
                            MinSize="600 600">
     <BoxContainer Orientation="Vertical" Margin="5 0 5 0">
@@ -65,4 +65,4 @@
         </PanelContainer>
         <TextureButton VerticalExpand="True" />
     </BoxContainer>
-</userInterface:FancyWindow>
+</controls:FancyWindow>