RFR(S) 8219370: NMT: Move synchronization primitives from mtInternal to mtSynchronizer

[zgu at redhat.com]

Please review this small patch that separates allocations for
synchronization primitives from mtInternal to mtSynchronizer, as a part
of efforts to further refine tracking categories.

Bug: https://bugs.openjdk.java.net/browse/JDK-8219370
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8219370/webrev.00/index.htm
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Test:
  hotspot_nmt on Linux x64 (fastdebug and release)
  JDK-submit

Thanks,

-Zhengyu