[jdk8u-dev] RFR: 8240189: [TESTBUG] Some cgroup tests are failing after JDK-8231111

[Jonathan Dowland]

This is a back port of 8240189: [TESTBUG] Some cgroup tests are failing after JDK-8231111
for jdk8u-dev as part of an effort to backport support for Cgroups V2.

The intention is for this PR to depend upon [8231111: 2Cgroups v2: Rework Metrics in java.base so as to recognize unified hierarchy](https://github.com/openjdk/jdk8u-dev/pull/121), which in turn depends upon [8206456: [TESTBUG] docker jtreg tests fail on systems without cpuset.effective_cpus / cpuset.effective_mems](https://github.com/openjdk/jdk8u-dev/pull/123), both of which are dependencies for this patch-set.

This backport is one commit on top of pr/121. It does not apply clean after path unshuffling: some of the patch contexts around `MetricsMemoryTester.java`,  `MetricsTesterCgroupV1.java` and  `MetricsTesterCgroupV2.java` differ due to changes made in pr/121 to adjust for jdk8u-dev support (replacing `Arrays.compare` with `Arrays.equals`)

I'll report back testing results to this PR, I have to untangle them a bit first.

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Depends on: https://git.openjdk.org/jdk8u-dev/pull/121

Commit messages:
 - 8240189: [TESTBUG] Some cgroup tests are failing after JDK-8231111

Changes: https://git.openjdk.org/jdk8u-dev/pull/124/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=124&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8240189
  Stats: 145 lines in 5 files changed: 46 ins; 28 del; 71 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/124.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/124/head:pull/124

PR: https://git.openjdk.org/jdk8u-dev/pull/124