RFR: 7903055: Replace `junit.jar` with `junit-platform-console-standalone` artifact

[Christian Stein]

https://bugs.openjdk.java.net/browse/CODETOOLS-7903055

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Commit messages:
 - 7903055: Replace `junit.jar` with `junit-platform-console-standalone` artifact

Changes: https://git.openjdk.java.net/jtreg/pull/40/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=40&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903055
  Stats: 88 lines in 9 files changed: 3 ins; 75 del; 10 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/40.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/40/head:pull/40

PR: https://git.openjdk.java.net/jtreg/pull/40