Allow having nested Docker-based tests

@UITest(office = true, servletEngine = ServletEngine.TOMCAT,
    forbiddenEngines = {
        // These tests need to have XWiki running inside a Docker container (we chose Tomcat since it's the most
        // used one), because they need LibreOffice to be installed, and we cannot guarantee that it is installed on the
        // host machine.
        ServletEngine.JETTY_STANDALONE
    },
    properties = {
        // Overridden to add the FileUploadPlugin which is needed by the test to upload some office files to import
        "xwikiCfgPlugins=com.xpn.xwiki.plugin.skinx.JsSkinExtensionPlugin,"
            + "com.xpn.xwiki.plugin.skinx.JsSkinFileExtensionPlugin,"
            + "com.xpn.xwiki.plugin.skinx.CssSkinExtensionPlugin,"
            + "com.xpn.xwiki.plugin.skinx.CssSkinFileExtensionPlugin,"
            + "com.xpn.xwiki.plugin.skinx.LinkExtensionPlugin,"
            + "com.xpn.xwiki.plugin.fileupload.FileUploadPlugin"
    }
)
public class AllIT
{
    @Nested
    @DisplayName("Office Import Tests")
    class NestedOfficeImporterIT extends OfficeImporterIT
    {
    }
}