[jdk11u-dev] RFR: 8231111: Cgroups v2: Rework Metrics in java.base so as to recognize unified hierarchy [v2]

[Zhengyu Gu]

> This is a followup backport for Cgroup v2 support.
> 
> The original patch does not apply cleanly, due to context differences and some of out-of-order backports, conflicts were resolved manually.
> 
> In additional:
> 
> 1) Include partial backport of JDK-8250627.
>     - Renamed `Metrics.c` =>  `CgroupMetrics.c`
>     - Added native method `isUseContainerSupport()` to `CgroupMetrics.java`
>     - Return instance only if `isUseContainerSupport()` is enabled.
>    
> 2) Add `createTempDirectory()` method to `test/lib/jdk/test/lib/Utils.java` for `TestCgroupSubsystemController.java` test
> 
> 3) Add `import jdk.test.lib.process.OutputAnalyzer;` to `TestDockerMemoryMetrics.java`
> 
> Test:
> 
> - [x] jtreg containers/docker test on Ubuntu 20.04.4 LTS
> - [x] jdk/internal/platform/cgroup on Ubuntu 20.04.4 LTS
> - [x] jdk/internal/platform/docker on Ubuntu 20.04.4 LTS

Zhengyu Gu has updated the pull request incrementally with three additional commits since the last revision:

 - Redo CgroupV1Subsystem.java merge
 - Severin's comments - 2
 - Severin's comments

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

Changes:
  - all: https://git.openjdk.java.net/jdk11u-dev/pull/863/files
  - new: https://git.openjdk.java.net/jdk11u-dev/pull/863/files/f200bd77..d5d4fa02

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=863&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=863&range=00-01

  Stats: 127 lines in 5 files changed: 59 ins; 13 del; 55 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/863.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/863/head:pull/863

PR: https://git.openjdk.java.net/jdk11u-dev/pull/863