RFR: 7903047: Make JUnit runner use the JUnit Platform Launcher [v2]

[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 incrementally with one additional commit since the last revision:

  Include JUnit Jupiter test

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

Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/78/files
  - new: https://git.openjdk.java.net/jtreg/pull/78/files/5110e470..ed9a76aa

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=78&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=78&range=00-01

  Stats: 12 lines in 2 files changed: 5 ins; 3 del; 4 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