Add generateHolderClasses(Stream<String>) for Java 16

[keithc-ca]

See https://ci.eclipse.org/openj9/job/Build_JDKnext_x86-64_linux_OpenJDK/282/:

22:23:40  /home/jenkins/workspace/Build_JDKnext_x86-64_linux_OpenJDK/src/java.base/share/classes/java/lang/invoke/MethodHandleImpl.java:1768: error: cannot find symbol
22:23:40                  return GenerateJLIClassesHelper.generateHolderClasses(traces);
22:23:40                                                 ^
22:23:40    symbol:   method generateHolderClasses(Stream<String>)
22:23:40    location: class GenerateJLIClassesHelper

[keithc-ca]

Jenkins compile xlinux jdknext depends ibmruntimes/openj9-openjdk-jdk#openj9-staging

[DanHeidinga]

lgtm