RFR: 7903324: Improve per-class reporting of JUnit tests, in .jtr file

[Christian Stein]

Improve per-class reporting of JUnit tests by using a custom `TestExecutionListener` in `JUnitRunner`.

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Commit messages:
 - Run JUnit trace self-test as an initial test
 - Fix build
 - Address feedback from reviewers
 - Merge branch 'openjdk:master' into 7903324-improve-junit-per-class-reporting
 - Improve readability by refactoring launcher configuration and extracting summary rendering
 - Capture messages printed to standard streams by default
 - Address review comments
 - Improve per-class reporting of JUnit tests

Changes: https://git.openjdk.org/jtreg/pull/127/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=127&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903324
  Stats: 153 lines in 2 files changed: 114 ins; 31 del; 8 mod
  Patch: https://git.openjdk.org/jtreg/pull/127.diff
  Fetch: git fetch https://git.openjdk.org/jtreg pull/127/head:pull/127

PR: https://git.openjdk.org/jtreg/pull/127