XWIKI-8687: Allow the user to specify the previously installed UI when upgrading from very old versions
* Reverse the version order (newest version at the top).
* Show the recommended UI extension if the specified previous UI extension is already installed.
* Don't show the previous UI form if the user has already started the (install) job for the recommended UI.
* The version select doesn't need a name because the version input is updated whenever a version is selected.