RFR: JDK-8324287: Record total and free swap space in JFR [v3]

[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:

  Adjust description, fix some indentation

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17581/files
  - new: https://git.openjdk.org/jdk/pull/17581/files/824f3bc5..a9114b1a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17581&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17581&range=01-02

  Stats: 19 lines in 3 files changed: 4 ins; 6 del; 9 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