RFR: 8342681: TestLoadBypassesNullCheck.java fails improperly specified VM option [v2]

[SendaoYan]

> Hi all,
> Newly added test `gc/shenandoah/compiler/TestLoadBypassesNullCheck.java` fails `The unlock option must precede 'StressGCM'.` with release jdk build. This PR fix the test bug, only add `-XX:+UnlockDiagnosticVMOptions` to make test run passed by release jdk build.
> The change has been verified locally with release/fastdebug/slowdebug on linux-x64. Test-fix only, no risk.

SendaoYan has updated the pull request incrementally with one additional commit since the last revision:

  only unlock Stress* VM option

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21609/files
  - new: https://git.openjdk.org/jdk/pull/21609/files/43731b9e..b7237e8e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21609&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21609&range=00-01

  Stats: 6 lines in 1 file changed: 2 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/21609.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21609/head:pull/21609

PR: https://git.openjdk.org/jdk/pull/21609