RFR: JDK-8315213: java/lang/ProcessHandle/TreeTest.java test enhance output of children [v2]

[Matthias Baesken]

> We have some failures in TreeTest.java where the expected number of child processes is differing from what we really get. It would be good to have more output to analyze these cases.

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

  use 2 containers for children and descendants

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15466/files
  - new: https://git.openjdk.org/jdk/pull/15466/files/fb420eab..07434cd8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15466&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15466&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15466.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15466/head:pull/15466

PR: https://git.openjdk.org/jdk/pull/15466