[appkit] Use generated bindings for NS[Open|Save].[Open|Save]Panel. Fixes #5336 (#5341)

Also add [Advice] to help people using writing applications that runs
inside the sandbox.

reference: https://github.com/xamarin/xamarin-macios/issues/5336

src/AppKit/NSOpenPanel.cs

@@ -1,21 +0,0 @@
-using System;
-using System.Collections.Generic;
-
-using Foundation;
-using ObjCRuntime;
-
-namespace AppKit
-{
-	public partial class NSOpenPanel
-	{
-		[Export ("openPanel")]
-		public static NSOpenPanel OpenPanel {
-			get {
-				// [NSOpenPanel openPanel] will always create a new instance, so there's no need to check if there already is
-				// a managed object with the same pointer.
-				IntPtr ptr = Messaging.IntPtr_objc_msgSend (Class.GetHandle ("NSOpenPanel"), Selector.GetHandle ("openPanel"));
-				return new NSOpenPanel (ptr);
-			}
-		}
-	}
-}

src/AppKit/NSSavePanel.cs

@@ -1,21 +0,0 @@
-using System;
-using System.Collections.Generic;
-
-using Foundation;
-using ObjCRuntime;
-
-namespace AppKit
-{
-	public partial class NSSavePanel
-	{
-		[Export ("savePanel")]
-		public static NSSavePanel SavePanel {
-			get {
-				// [NSSavePanel savePanel] will always create a new instance, so there's no need to check if there already is
-				// a managed object with the same pointer.
-				IntPtr ptr = Messaging.IntPtr_objc_msgSend (Class.GetHandle ("NSSavePanel"), Selector.GetHandle ("savePanel"));
-				return new NSSavePanel (ptr);
-			}
-		}
-	}
-}

src/appkit.cs

@@ -8643,7 +8643,17 @@ namespace AppKit {
 	}
 
 	[BaseType (typeof (NSSavePanel))]
+	[DisableDefaultCtor]
 	interface NSOpenPanel {
+		[Static]
+		[Export ("openPanel")]
+		[ForcedType] // different type used inside a sandbox
+		NSOpenPanel OpenPanel { get; }
+
+		[Advice ("You must use 'OpenPanel' method if the application is sandboxed.")]
+		[Export ("init")]
+		IntPtr Constructor ();
+
 		[Export ("URLs")]
 		NSUrl [] Urls { get; }
 
@@ -12896,7 +12906,17 @@ namespace AppKit {
 	delegate void NSSavePanelComplete (nint result);
 	
 	[BaseType (typeof (NSPanel), Delegates=new string [] { "Delegate" }, Events=new Type [] { typeof (NSOpenSavePanelDelegate)})]
+	[DisableDefaultCtor]
 	interface NSSavePanel {
+		[Static]
+		[Export ("savePanel")]
+		[ForcedType] // different type used inside a sandbox
+		NSSavePanel SavePanel { get; }
+
+		[Advice ("You must use 'SavePanel' method if the application is sandboxed.")]
+		[Export ("init")]
+		IntPtr Constructor ();
+
 		[Export ("URL")]
 		NSUrl Url { get; }
 

src/frameworks.sources

@@ -138,8 +138,6 @@ APPKIT_SOURCES = \
 	AppKit/NSTouch.cs \
 	AppKit/NSTreeController.cs \
 	AppKit/NSWindow.cs \
-	AppKit/NSOpenPanel.cs \
-	AppKit/NSSavePanel.cs \
 	AppKit/NSWorkspace.cs \
 	AppKit/NSCollectionView.cs \
 	AppKit/NSCollectionViewDelegate.cs \

tests/xtro-sharpie/macOS-AppKit.ignore

@@ -1128,9 +1128,7 @@
 !missing-selector! +NSBezierPath::bezierPath not bound
 !missing-selector! +NSCursor::pop not bound
 !missing-selector! +NSInputManager::currentInputManager not bound
-!missing-selector! +NSOpenPanel::openPanel not bound
 !missing-selector! +NSPDFPanel::panel not bound
-!missing-selector! +NSSavePanel::savePanel not bound
 !missing-selector! +NSSound::soundUnfilteredFileTypes not bound
 !missing-selector! +NSSound::soundUnfilteredPasteboardTypes not bound
 !missing-selector! NSBezierPath::cachesBezierPath not bound