RFR: 8322219: GenShen: GHA for shenandoah repo should run all shenandoah jtreg tests

[William Kemper]

8322219: GenShen: GHA for shenandoah repo should run all shenandoah jtreg tests

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Commit messages:
 - Backport 490ed34edd5c99aa132c0faa351da2ad5ae59577

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/7/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=7&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322219
  Stats: 5 lines in 1 file changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/7.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/7/head:pull/7

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/7