RFR: 8127: Use ProcessHandle API to get PIDs [v2]

[Christoph Dreis]

> Hi,
> 
> this PR uses `ProcessHandle.current().pid()` that was introduced in Java 9 rather than parsing the output of `ManagementFactory.getRuntimeMXBean().getName()`.
> 
> If you think this is worthwhile, I'd appreciate a ticket and sponsoring.
> 
> Cheers,
> Christoph

Christoph Dreis has updated the pull request incrementally with one additional commit since the last revision:

  8127: Remove obsolete try/catch in Environment

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

Changes:
  - all: https://git.openjdk.org/jmc/pull/522/files
  - new: https://git.openjdk.org/jmc/pull/522/files/db4fb8e8..e6f1343f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmc&pr=522&range=01
 - incr: https://webrevs.openjdk.org/?repo=jmc&pr=522&range=00-01

  Stats: 7 lines in 1 file changed: 0 ins; 6 del; 1 mod
  Patch: https://git.openjdk.org/jmc/pull/522.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/522/head:pull/522

PR: https://git.openjdk.org/jmc/pull/522