RFR: 8352299: GenShen: Young cycles that interrupt old cycles cannot be cancelled

[William Kemper]

The sequence of events that creates this state:
1. An old collection is trying to finish marking by flushing SATB buffers with a Handshake
2. The regulator thread cancels old marking to start a young collection
3. A mutator thread shortly follows and attempts to cancel the nascent young collection
4. Step `3` fails (because of this bug) and cancellation reason does _not_ become `allocation failure`
5. The mutator thread enters a tight loop in which it retries allocations without `waiting`
6. The mutator thread remains in the `thread_in_vm` state and prevents the VM thread from completing step `1`.

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Commit messages:
 - Allow young cycles that interrupt old cycles to be cancelled

Changes: https://git.openjdk.org/jdk/pull/24105/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24105&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352299
  Stats: 9 lines in 2 files changed: 7 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/24105.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24105/head:pull/24105

PR: https://git.openjdk.org/jdk/pull/24105