RFR: 8127: Use ProcessHandle API to get PIDs [v3]

[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 with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - 8127: Remove obsolete try/catch in Environment
 - Use ProcessHandle API to get PIDs

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Changes: https://git.openjdk.org/jmc/pull/522/files
 Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=522&range=02
  Stats: 75 lines in 4 files changed: 0 ins; 70 del; 5 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