Various UI warnings cleanup (#36169)

* Various UI warnings cleanup

* Revert unnecessary change

* Redoing SpriteSystem as it's non-injectable

* Missed one

* Better entity instantiation

* General cleanup of warnings changes

* Wrong class name!

Content.Client/UserInterface/Systems/Storage/Controls/StorageWindow.cs

@@ -1,4 +1,4 @@
-using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Numerics;
 using Content.Client.Hands.Systems;