Monitor class should use ThreadBlockInVMPreprocess

JDK-8265753 added ThreadBlockInVMPreprocess as a more general class of ThreadBlockInVM that can take a call-back to be executed before possibly executing SafepointMechanism::process_if_requested().
This class should also be used in the Monitor class instead of using ThreadBlockInVM. This will allow to remove the embedded InFlightMutexRelease object from ThreadBlockInVM and to move the InFlightMutexRelease class definition to mutex.cpp where it belongs.