Revert "add a way to render to canvas with DrawingContext with public api"

This reverts commit e893705823.

src/Skia/Avalonia.Skia/ExternalCanvasRenderTarget.cs

@@ -1,32 +0,0 @@
-using Avalonia.Platform;
-using Avalonia.Rendering;
-
-namespace Avalonia.Skia
-{
-    internal class ExternalCanvasRenderTarget : IRenderTarget
-    {
-        private IExternalCanvasSurface _surface;
-
-        public ExternalCanvasRenderTarget(IExternalCanvasSurface canvas)
-        {
-            _surface = canvas;
-        }
-
-        public IDrawingContextImpl CreateDrawingContext(IVisualBrushRenderer visualBrushRenderer)
-        {
-            var createInfo = new DrawingContextImpl.CreateInfo
-            {
-                Canvas = _surface.Canvas,
-                Dpi = _surface.Dpi,
-                VisualBrushRenderer = visualBrushRenderer,
-                DisableTextLcdRendering = true,
-            };
-
-            return new DrawingContextImpl(createInfo);
-        }
-
-        public void Dispose()
-        {
-        }
-    }
-}

src/Skia/Avalonia.Skia/IExternalCanvasSurface.cs

@@ -1,11 +0,0 @@
-using SkiaSharp;
-
-namespace Avalonia.Skia
-{
-    public interface IExternalCanvasSurface
-    {
-        SKCanvas Canvas { get; }
-
-        Vector Dpi { get; }
-    }
-}

src/Skia/Avalonia.Skia/PlatformRenderInterface.cs

@@ -145,8 +145,6 @@ namespace Avalonia.Skia
             {
                 if (surface is IFramebufferPlatformSurface framebufferSurface)
                     return new FramebufferRenderTarget(framebufferSurface);
-                if (surface is IExternalCanvasSurface canvas)
-                    return new ExternalCanvasRenderTarget(canvas);
             }
 
             throw new NotSupportedException(