Introduce DrawingContextHelper.RenderAsync method (#13128)

#Conflicts:
#	src/Skia/Avalonia.Skia/Helpers/DrawingContextHelper.cs

src/Skia/Avalonia.Skia/Helpers/DrawingContextHelper.cs

@@ -1,4 +1,8 @@
-using Avalonia.Platform;
+using System.Diagnostics.CodeAnalysis;
+using System.Threading.Tasks;
+using Avalonia.Media;
+using Avalonia.Metadata;
+using Avalonia.Platform;
 using Avalonia.Rendering;
 using SkiaSharp;
 
@@ -6,14 +10,38 @@ namespace Avalonia.Skia.Helpers
 {
     public static class DrawingContextHelper
     {
+        /// <inheritdoc cref="RenderAsync(SKCanvas, Visual, Rect, Vector)"/>.
+        public static Task RenderAsync(SKCanvas canvas, Visual visual)
+        {
+            return RenderAsync(canvas, visual, visual.Bounds, SkiaPlatform.DefaultDpi);
+        }
+
+        /// <summary>
+        /// Renders Avalonia visual into a SKCanvas instance.
+        /// This is useful in scenarios where canvas is not controlled by application, but received from another non avalonia api
+        /// like: SKCanvas canvas = SKDocument.BeginPage(...);
+        /// </summary>
+        /// <param name="canvas">Skia canvas to render into.</param>
+        /// <param name="visual">Avalonia visual.</param>
+        /// <param name="clipRect">Clipping rectangle.</param>
+        /// <param name="dpi">Dpi of drawings.</param>
+        public static Task RenderAsync(SKCanvas canvas, Visual visual, Rect clipRect, Vector dpi)
+        {
+            using var drawingContextImpl = WrapSkiaCanvas(canvas, dpi);
+            using var drawingContext = new PlatformDrawingContext(drawingContextImpl, false);
+            ImmediateRenderer.Render(drawingContext, visual, clipRect);
+            return Task.CompletedTask;
+        }
+
         /// <summary>
         /// Wrap Skia canvas in drawing context so we can use Avalonia api to render to external skia canvas
         /// this is useful in scenarios where canvas is not controlled by application, but received from another non avalonia api
         /// like: SKCanvas canvas = SKDocument.BeginPage(...);
         /// </summary>
-        /// <param name="canvas"></param>
+        /// <param name="canvas">Skia canvas to render into.</param>
         /// <param name="dpi"></param>
         /// <returns>DrawingContext</returns>
+        [Unstable("IDrawingContextImpl usage is not supported in Avalonia 11.0.")]
         public static IDrawingContextImpl WrapSkiaCanvas(SKCanvas canvas, Vector dpi)
         {
             var createInfo = new DrawingContextImpl.CreateInfo