RFR: 8365065: cancelled ForkJoinPool tasks no longer throw CancellationException

[Viktor Klang]

ForkJoinTask::get and ForkJoinTask::get(timeout, timeunit) now (again) throws CancellationException when cancelled.

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Commit messages:
 - Makes ForkJoinTask::get throw CancellationException on cancellation

Changes: https://git.openjdk.org/jdk/pull/27430/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27430&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365065
  Stats: 81 lines in 2 files changed: 71 ins; 6 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/27430.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27430/head:pull/27430

PR: https://git.openjdk.org/jdk/pull/27430