RFR: 8203359: Container level resources events [v8]

[Jaroslav Bachorik]

> With this change it becomes possible to surface various cgroup level metrics (available via `jdk.internal.platform.Metrics`) as JFR events.
> 
> Only a subset of the metrics exposed by `jdk.internal.platform.Metrics` is turned into JFR events to start with.
> * CPU related metrics
> * Memory related metrics
> * I/O related metrics
> 
> For each of those subsystems a configuration data will be emitted as well. The initial proposal is to emit the configuration data events at least once per chunk and the metrics values at 30 seconds interval. 
> By using these values the emitted events seem to contain useful information without increasing overhead (the metrics values are read from `/proc` filesystem so that should not be done too frequently).

Jaroslav Bachorik has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 11 additional commits since the last revision:

 - Roll back conditional registration of container events
 - Remove container events flag
 - Remove trailing spaces
 - Doh
 - Report container type and register events conditionally
 - Remove unused test files
 - Initial test support for JFR container events
 - Update the JFR control files
 - Split off the CPU throttling metrics
 - Formatting spaces
 - ... and 1 more: https://git.openjdk.java.net/jdk/compare/faed1f5b...67a61bd7

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3126/files
  - new: https://git.openjdk.java.net/jdk/pull/3126/files/f4372e23..67a61bd7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3126&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3126&range=06-07

  Stats: 76531 lines in 2761 files changed: 49167 ins; 17238 del; 10126 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3126.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3126/head:pull/3126

PR: https://git.openjdk.java.net/jdk/pull/3126