RFR: JDK-8324287: Record total and free swap space in JFR [v2]

[Matthias Baesken]

> Total and free swap space should be recorded in JFR, because it is important to know e.g. in case of memory shortages.
> 
> Currently we only have a container related event (ContainerMemoryUsage) that provides some info but no general event.
> PhysicalMemory could be enhanced or a new event added.
> 
> There is already some coding (see Java_com_sun_management_internal_OperatingSystemImpl_getTotalSwapSpaceSize0 and
> Java_com_sun_management_internal_OperatingSystemImpl_getFreeSwapSpaceSize0) for the swap space info retrieval.

Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:

  remove comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17581/files
  - new: https://git.openjdk.org/jdk/pull/17581/files/466aed6c..824f3bc5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17581&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17581&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17581.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17581/head:pull/17581

PR: https://git.openjdk.org/jdk/pull/17581