XWIKI-22886: Jetty 12+ docker image is actually still not supported in 16.4.x

xwiki-platform-core/xwiki-platform-web/xwiki-platform-web-war/src/main/webapp/WEB-INF/jetty-ee8-web.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "https://www.eclipse.org/jetty/configure_9_0.dtd">
+
+<!--
+ * See the NOTICE file distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+-->
+
+<Configure class="org.eclipse.jetty.ee8.webapp.WebAppContext">
+  <!-- In order to avoid getting a "java.lang.IllegalStateException: Form too large" error when editing large page in
+       XWiki we need to tell Jetty to allow for large content since by default it only allows for 20K. We do this by
+       passing the "org.eclipse.jetty.server.Request.maxFormContentSize" attribute.
+       Note 1: Setting this value too high can leave your server vulnerable to denial of service attacks.
+       Note 2: We're setting it here instead of in Jetty's XML configuration files so that the XWiki WAR can be used
+       in any Jetty config and work out of the box.
+  -->
+  <Set name="maxFormContentSize">1000000</Set>
+  <!-- Increasing the maxFormKeys in order to be able to import correctly a full wiki (more than 1000 pages in 11.10).
+       The import should be fixed at a point to allow importing everything without creating a form with a field by 
+       page. Once done this configuration can be removed. See https://jira.xwiki.org/browse/XWIKI-11597 for a follow 
+       up. 
+  -->
+  <Set name="maxFormKeys">2000</Set>
+</Configure>