RFR: 8292541: [Metrics] Reported memory limit may exceed physical machine memory

[Jonathan Dowland]

When the container memory exceeds the physical host's memory, the Java metrics reporting is wrong.

https://bugs.openjdk.org/browse/JDK-8292541

This is the equivalent core-libs fix for Hotspot's [JDK-8292083](https://bugs.openjdk.org/browse/JDK-8292083)
(https://github.com/openjdk/jdk/pull/9880)

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Commit messages:
 - catch CgroupMetrics.getMemoryLimit exceeding physical RAM
 - Add two tests to catch deriving invalid max memory limit from cgroups

Changes: https://git.openjdk.org/jdk/pull/10017/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10017&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292541
  Stats: 47 lines in 3 files changed: 47 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10017.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10017/head:pull/10017

PR: https://git.openjdk.org/jdk/pull/10017