RFR: 7903047: Make JUnit runner use the JUnit Platform Launcher [v16]

[Christian Stein]

> Make JUnit runner use the JUnit Platform Launcher
> 
> See https://bugs.openjdk.java.net/browse/CODETOOLS-7903047

Christian Stein has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 18 additional commits since the last revision:

 - Merge branch 'openjdk:master' into 7903047-junit-with-platform-launcher
 - Fix typo
 - Run in `agent` and `other` VM mode
 - Address review comments
 - Add support for `runWithJUnit4` flag
 - Replace one last `var` usage
 - Agent's sources target Java SE release 8
 - Remove JUnit Trace test from set of initial tests
 - Check usage of standard and parameterized Jupiter API
 - Fix typo
 - ... and 8 more: https://git.openjdk.java.net/jtreg/compare/a48a35db...5133c93f

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

Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/78/files
  - new: https://git.openjdk.java.net/jtreg/pull/78/files/4fe0743c..5133c93f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=78&range=15
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=78&range=14-15

  Stats: 35 lines in 11 files changed: 4 ins; 3 del; 28 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/78.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/78/head:pull/78

PR: https://git.openjdk.java.net/jtreg/pull/78