[11u] RFR 8219370: NMT: Move synchronization primitives from mtInternal to mtSynchronizer

[Zhengyu Gu]

Hi,

I would like to backport this patch to 11u.

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

The patch does not apply cleanly, due to:
1) PlatformMonitors are no longer in 11u code base
2) JDK-8210246 changed how new memory category is defined, and it does 
not look like in 11u backport list.

Original bug: https://bugs.openjdk.java.net/browse/JDK-8219370
Original webrev: http://cr.openjdk.java.net/~zgu/JDK-8219370/webrev.00/


11u Webrev: 
http://cr.openjdk.java.net/~zgu/JDK-8219370-11u/webrev.00/index.html

Test:
   hotspot_nmt (fastdebug and release) on Linux 86_64.

Thanks,

-Zhengyu