RFR: 8252921: NMT overwrite memory type for region assert when building dynamic archive

[Zhengyu Gu]

Thread stack is currently unregistered with NMT in Thread's destructor. Apparently, only Java thread invokes destructor
before thread exits.  For NonJavaThread, e.g. ConcurrentGCThread, thread may exit while its "Thread" object continues
alive, therefore, its thread stack is still "alive" from NMT perspective. Once thread exits, the virtual memory for the
thread stack can be reserved again, that confused NMT.

The solution is to move thread stack unregistration code to post_run() method.

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Commit messages:
 - JDK-8252921
 - JDK-8252921

Changes: https://git.openjdk.java.net/jdk/pull/185/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=185&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252921
  Stats: 24 lines in 2 files changed: 10 ins; 13 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/185.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/185/head:pull/185

PR: https://git.openjdk.java.net/jdk/pull/185