Change to behavior matching System.Drawing.Rectangle

Terminal.Gui/Types/Rectangle.cs

@@ -287,5 +287,5 @@ public struct Rectangle
 
     /// <summary>ToString Method</summary>
     /// <remarks>Formats the Rectangle as a string in (x,y,w,h) notation.</remarks>
-    public override string ToString () { return $"({X},{Y},{Width},{Height})"; }
+    public override string ToString () { return $"{{X={X},Y={Y},Width={Width},Height={Height}}}"; }
 }

UnitTests/Types/RectangleTests.cs

@@ -513,7 +513,7 @@ public class RectangleTests
     public void ToString_ReturnsExpectedString ([CombinatorialValues(-1,0,1)]int x, [CombinatorialValues(-1,0,1)]int y, [CombinatorialValues(1,10)]int width, [CombinatorialValues(1,10)]int height)
     {
         Rectangle r = new (x, y, width, height);
-        string expectedString = $"({r.X},{r.Y},{r.Width},{r.Height})";
+        string expectedString = $"{{X={r.X},Y={r.Y},Width={r.Width},Height={r.Height}}}";
         Assert.Equal (expectedString, r.ToString ());
     }
 }