RFR: 8359870: JVM crashes in AccessInternal::PostRuntimeDispatch [v2]

[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 one additional commit since the last revision:

  ThreadDumper thread count

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25958/files
  - new: https://git.openjdk.org/jdk/pull/25958/files/33248d9d..e4a7b546

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25958&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25958&range=00-01

  Stats: 11 lines in 1 file changed: 6 ins; 0 del; 5 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