[jdk21u-dev] RFR: 8333446: Add tests for hierarchical container support

[Severin Gehwolf]

Please review this test-only backport. Now that https://bugs.openjdk.org/browse/JDK-8322420 is in jdk21u-dev it makes sense to automatically test this functionality. The patch is clean except for the changes in `VMProps.java` which I've added manually.

The only non-test tree change is to `whitebox.cpp`.

Testing:
- [x] GHA
- [x] container tests on Linux x86 with cgroups v2 and cgroups v1

Thoughts?

Note: I'll follow up with [JDK-8340092](https://bugs.openjdk.org/browse/JDK-8340092) once this is in.

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Commit messages:
 - Backport d9fdf69c34c20e0f2d526c2f04450acb904c3e80

Changes: https://git.openjdk.org/jdk21u-dev/pull/1938/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1938&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333446
  Stats: 655 lines in 9 files changed: 648 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1938.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1938/head:pull/1938

PR: https://git.openjdk.org/jdk21u-dev/pull/1938