RFR: 8296125: Add a command line option to set a refresh rate of the OS cached metrics in Linux [v2]

[Olga Mikhaltsova]

> I would like to add a new command line product option:
> -XX:OsCachedMetricsRefreshRate=value, -
> where a value is times per second and is in the range [1; 1000000000].
> 
> It substitutes the hardcoded timeout of 20 ms between re-readings of the OS cached metrics introduced in [JDK-8232207](https://bugs.openjdk.org/browse/JDK-8232207) and allows to set this timeout (as a refresh rate) by a user at the launch time.
> 
> This option will be available only on Linux.
> 
> It can be used as followed:
> java -XX:OsCachedMetricsRefreshRate=100 MyApp

Olga Mikhaltsova has updated the pull request incrementally with two additional commits since the last revision:

 - Made the option (OsCachedMetricsRefreshRate) DIAGNOSTIC
 - Moved oscontainer_cache_timeout() from os::Linux to OSContainer

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10918/files
  - new: https://git.openjdk.org/jdk/pull/10918/files/8e367434..51fa4d73

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10918&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10918&range=00-01

  Stats: 15 lines in 6 files changed: 6 ins; 6 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/10918.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10918/head:pull/10918

PR: https://git.openjdk.org/jdk/pull/10918