Not all fields are shown in the Sidebar

If a field is set to be displayed in the sidebar, (has the ['#group'] = 'advanced'), it's not respected by Gutenberg

An example would be the Metatag field.

Steps to reproduce:

1. Install metatag module
2. Add a metatag field on the content type where the Gutenberg editor is enabled
3. Set from Manage form Display Use sidebar: TRUE (this is an option for the metatag field, which will add the ['#group'] = 'advanced' key on form element
4. Create / edit content

You will see that the Metatag field is displayed below the Gutenberg editor and not in the sidebar.

I created a patch which fixes this issue