When menu items are dynamically added to Menu, it should resize to fit

With the approach taken in https://codereview.qt-project.org/c/qt/qtdeclarative/+/632999 to customize a TextArea's default context menu:

Component.onCompleted: {
...
  const menu = textArea.ContextMenu.menu
  menu.addItem(menuSeparatorComponent.createObject(menu.contentItem))
  menu.addAction(fontDialogAction)
  menu.addAction(colorDialogAction)
}

it seems the existing ContextMenu was "styled" according to the items it had at the beginning. On some styles, when new items are added, the menu becomes scrollable, which looks odd (and it's not even obvious that there are more menu items until you attempt scrolling). Probably it should get resized so that they fit.

Fusion, Universal, Material, and Basic styles are all fine. macOS and FluentWinUI3 styles are doing this scrolling within the menu.