RFR: 8333930: GenShen: Check for cancellation of old mark after final mark

[William Kemper]

This is the old generation mark version of https://github.com/openjdk/jdk/pull/19434

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Commit messages:
 - Check for cancellation after final mark

Changes: https://git.openjdk.org/shenandoah/pull/448/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=448&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333930
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/shenandoah/pull/448.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/448/head:pull/448

PR: https://git.openjdk.org/shenandoah/pull/448