[jdk11u-dev] RFR: 8254001: [Metrics] Enhance parsing of cgroup interface files for version detection

[Andrew Azores]

Backport commit [a50725db2ab621e1a17cb5505f78e4bc73972a27](https://github.com/openjdk/jdk/commit/a50725db) for [JDK-8254001](https://bugs.openjdk.java.net/browse/JDK-8254001), enhancement to cgroups interface parsing and version detection.

The patch applied mostly cleanly with only two minor conflicts in `CgroupV1Subsystem.java`. These conflicts were simply hunks that failed to apply because the surrounding context did not match due to later changes in the internal implementation that are not present in JDK11. Since the patch being backported wholly replaces or removes these implementations anyway, my resolution was to simply remove the old implementation and accept the new implementation from the backport patch.

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Commit messages:
 - Partial backport of 4d6593ce0243457e7431a5990957a8f880e0a3fb
 - Backport a50725db2ab621e1a17cb5505f78e4bc73972a27

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/1020/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=1020&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254001
  Stats: 595 lines in 5 files changed: 321 ins; 142 del; 132 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/1020.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/1020/head:pull/1020

PR: https://git.openjdk.java.net/jdk11u-dev/pull/1020