XWIKI-20116: Upgrade to Jetty 10.0.15

...-tool-jetty/xwiki-platform-tool-jetty-resources/README.md

...rm-tool-jetty/xwiki-platform-tool-jetty-resources/pom.xml

...sources/src/main/resources/jetty/etc/jetty-threadpool.xml

...ol-jetty-resources/src/main/resources/jetty/etc/jetty.xml

...tty-resources/src/main/resources/jetty/etc/webdefault.xml

...resources/src/main/resources/jetty/modules/apache-jsp.mod

...tty-resources/src/main/resources/jetty/modules/server.mod

...resources/src/main/resources/jetty/modules/threadpool.mod