RFR: 8319935: Ensure only one JvmtiThreadState is create for one JavaThread associated with attached native thread

[Jiangli Zhou]

Please review JvmtiThreadState::state_for_while_locked change to handle the state->get_thread_oop() null case. Please see https://bugs.openjdk.org/browse/JDK-8319935 for details.

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Commit messages:
 - 8319935: Ensure only one JvmtiThreadState is create for one JavaThread associated with attached native thread

Changes: https://git.openjdk.org/jdk/pull/16642/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16642&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319935
  Stats: 14 lines in 1 file changed: 9 ins; 4 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16642.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16642/head:pull/16642

PR: https://git.openjdk.org/jdk/pull/16642