RFR: 8341261: Tests assume UnlockExperimentalVMOptions is disabled by default

[Todd V. Jonker]

`-UnlockExperimentalVMOptions` isn't necessarily the default: a distro may enable it in order to default-enable other features like JVMCI/Graal.

I'm not entirely satisfied by adding a `@require` that only applies to a subset of the checks in a test class.  In `VMOptionWarning`, the experimental flag only applies to the first of the three scenarios it checks.  But I suspect this is a general problem with `@require`, and I'd be happy to hear suggestions on how to avoid disabling too much.

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Commit messages:
 - Tests assume UnlockExperimentalVMOptions is disabled by default.

Changes: https://git.openjdk.org/jdk/pull/21233/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21233&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341261
  Stats: 11 lines in 4 files changed: 11 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21233.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21233/head:pull/21233

PR: https://git.openjdk.org/jdk/pull/21233