RFR: 7903047: Make JUnit runner use the JUnit Platform Launcher [v14]

[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:

  Run in `agent` and `other` VM mode

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

Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/78/files
  - new: https://git.openjdk.java.net/jtreg/pull/78/files/fff3c159..b2e0fd27

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=78&range=13
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=78&range=12-13

  Stats: 6 lines in 1 file changed: 3 ins; 0 del; 3 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