RFR (S) 8222893: markOopDesc::print_on() is a bit confused

[coleen.phillimore at oracle.com]

Summary: Add print_on for ObjectMonitor and make markOop printing 
sensible and add test.

Testing with mach5 ongoing, but tested locally.

open webrev at http://cr.openjdk.java.net/~coleenp/2019/8222893.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8222893

Thanks,
Coleen