RFR: 8319935: Ensure only one JvmtiThreadState is create for one JavaThread associated with attached native thread [v5]

[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.

Jiangli Zhou has updated the pull request incrementally with one additional commit since the last revision:

  Address Serguei Spitsyn's comments/suggestions:
  - Remove the redundant thread->is_Java_thread() check from JvmtiSampledObjectAllocEventCollector::object_alloc_is_safe_to_sample().
  - Change the assert in JvmtiThreadState::state_for_while_locked to avoid #ifdef ASSERT.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16642/files
  - new: https://git.openjdk.org/jdk/pull/16642/files/de7fac6d..7c366df0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16642&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16642&range=03-04

  Stats: 12 lines in 2 files changed: 0 ins; 5 del; 7 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