[jdk8u-dev] RFR: 8284102: [TESTBUG] [11u] Retroactively add regression test for JDK-8272124 [v2]

[Jonathan Dowland]

> Backport of 8284102 for jdk8u-dev for cgroups v2 support. Not clean, needed `Files.writeString` adjustment. Test builds and passes for me afterwards.

Jonathan Dowland has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - adjust Files.writeString→write for jdk8u
 - 8284102: [TESTBUG] [11u] Retroactively add regression test for JDK-8272124
   
   Reviewed-by: andrew
 - 8284756: [11u] Remove unused isUseContainerSupport in CgroupV1Subsystem
 - Add a macosx platform specific SystemMetrics class

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

Changes:
  - all: https://git.openjdk.org/jdk8u-dev/pull/179/files
  - new: https://git.openjdk.org/jdk8u-dev/pull/179/files/391d4203..9377fbd9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=179&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=179&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/179.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/179/head:pull/179

PR: https://git.openjdk.org/jdk8u-dev/pull/179