Update NSImage with changes made to bitmap pixel data

In order to get access to wxBitmap's pixel data we actually have to work
with CGBitmapContext data and this context is created from NSImage by call
to wxBitmapRefData::EnsureBitmapExists() when we prepare to get access
to the data in wxBitmapRefData::GetRawAccess().
So, when we finish updating bitmap data we should update original NSImage
with actual CGBitmapContext data in wxBitmapRefData::EndRawAccess().

See #18606.

src/osx/core/bitmap.cpp

@@ -419,6 +419,15 @@ void wxBitmapRefData::EndRawAccess()
     wxASSERT( m_rawAccessCount == 1 ) ;
 
     --m_rawAccessCount ;
+
+    // Update existing NSImage with new bitmap data
+    if ( m_nsImage )
+    {
+        wxCFRef<CGImageRef> image(CGBitmapContextCreateImage(m_hBitmap));
+        wxMacCocoaRelease(m_nsImage);
+        m_nsImage = wxOSXGetImageFromCGImage(image, GetScaleFactor(), IsTemplate());
+        wxMacCocoaRetain(m_nsImage);
+    }
 }
 
 bool wxBitmapRefData::HasNativeSize()