[jdk17u-dev] RFR: 8303742: CompletableFuture.orTimeout leaks if the future completes exceptionally

[Ben Taylor]

Clean backport of a patch to prevent `CompleteableFuture.orTimeout` from leaking when a `ScheduledFutureTask` exits exceptionally

Passes the included test as well as jtreg tier 1 locally on linux x86_64

-------------

Commit messages:
 - Backport ded6a8131970ac2f7ae59716769e6f6bae3b809a

Changes: https://git.openjdk.org/jdk17u-dev/pull/3000/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3000&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303742
  Stats: 64 lines in 2 files changed: 63 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3000.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3000/head:pull/3000

PR: https://git.openjdk.org/jdk17u-dev/pull/3000