Calling AccessibilityHandler::getChildren() or getParent() may cause an AccessibilityHandler object to be created and an InternalAccessibilityEvent::elementCreated notification to be sent. Calling AndroidAccessibilityEvent.setSource may then cause a recursive populateNodeInfo() call.

Sometimes, changing the bounds of the window inside the DPICHANGED
handler can cause further DPI change events to be processed. Previously,
the scaleFactor set by the "inner" events was also being used when
notifying listeners about the "outer" events, leading to graphical
glitches.

An effect of the bug was that VST2 views in the AudioPluginHost would
occasionally render with an incorrect size and position after dragging
them between displays with different scale factors.

With this change in place, we only notify listeners and update window
bounds once there are no DPI changes in progress.

- Add AlertWindow::show() and showAsync() methods that take a MessageBoxOptions argument
  - Add NativeMessageBox::show() and showAsync() methods that take a MessageBoxOptions argument
  - Update the DialogsDemo to demonstrate the new methods
  - Deprecate AlertWindow::showNativeDialogBox() in favour of the NativeMessageBox methods
  - Pass button strings specified in MesssageBoxOptions to native dialog boxes correctly
  - Use modern TaskDialog on Windows for the native dialog box where available