RFR: 8359870: JVM crashes in AccessInternal::PostRuntimeDispatch [v9]

[Kevin Walls]

> ThreadDumper/ThreadSnapshot need to handle a failure to resolve the native VM JavaThread from a java.lang.Thread.  This is hard to reproduce but a thread that has since terminated can provoke a crash.  Recognise this and return a null ThreadSnapshot.

Kevin Walls has updated the pull request incrementally with two additional commits since the last revision:

 - Merge branch '8359870_threadexited' of https://github.com/kevinjwalls/jdk into 8359870_threadexited
 - Feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25958/files
  - new: https://git.openjdk.org/jdk/pull/25958/files/d56e9d16..93ad155d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25958&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25958&range=07-08

  Stats: 3 lines in 3 files changed: 1 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25958.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25958/head:pull/25958

PR: https://git.openjdk.org/jdk/pull/25958