[8u] RFR 8219370: NMT: Move synchronization primitives from mtInternal to mtSynchronizer

[Zhengyu Gu]

I would like to backport this patch to 8u.

This patch aggregated synchronization primitives under a new memory 
category, which improves NMT usability.

The patch does not apply cleanly, due to:
1) PlatformMonitor is not in 8u code base
2) PlatformEvent and PlatformParker have yet been factored out to Posix 
for compliant OSs
3) semaphore is defined as StackObj in 8u
4) Memory type declaration is not compatible

Original bug: https://bugs.openjdk.java.net/browse/JDK-8219370
original code review: 
https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2019-February/032684.html


8u Webrev: 
http://cr.openjdk.java.net/~zgu/JDK-8219370-8u/webrev.00/index.html

Thanks,

-Zhengyu