Eclipse Jetty HTTP clients can increase memory allocation

In Eclipse Jetty versions 12.0.0 to 12.0.16 included, an HTTP/2 client can specify a very large value for the HTTP/2 settings parameter SETTINGS_MAX_HEADER_LIST_SIZE. The Jetty HTTP/2 server does not perform validation on this setting, and tries to allocate a ByteBuffer of the specified capacity to encode HTTP responses, likely resulting in OutOfMemoryError being thrown, or even the JVM process exiting.