[jdk8u-dev] RFR: 8254001: [Metrics] Enhance parsing of cgroup interface files for version detection

[Jonathan Dowland]

This is a backport of 8254001 to jdk8u-dev for cgroups v2 support.

It's not clean: some context issues around import lines and `Files.writeString` replacements.

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Depends on: https://git.openjdk.org/jdk8u-dev/pull/169

Commit messages:
 - 8254001: [Metrics] Enhance parsing of cgroup interface files for version detection

Changes: https://git.openjdk.org/jdk8u-dev/pull/170/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=170&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8254001
  Stats: 595 lines in 5 files changed: 321 ins; 142 del; 132 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/170.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/170/head:pull/170

PR: https://git.openjdk.org/jdk8u-dev/pull/170