[jdk8u-dev] RFR: 8254001: [Metrics] Enhance parsing of cgroup interface files for version detection [v2]

[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.

Jonathan Dowland has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - 8254001: [Metrics] Enhance parsing of cgroup interface files for version detection
   
   Reviewed-by: sgehwolf
   Backport-of: a50725db2ab621e1a17cb5505f78e4bc73972a27
 - 8253797: [cgroups v2] Account for the fact that swap accounting is disabled on some systems
   
   Backport-of: 669361117d30c9904813b6f728714f8d6abe8484

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Changes: https://git.openjdk.org/jdk8u-dev/pull/170/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=170&range=01
  Stats: 636 lines in 6 files changed: 341 ins; 139 del; 156 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