RFR: JDK-8266254: Update to use jtreg 6

[Jonathan Gibbons]

Please review the change to update to using jtreg 6. 

The primary change is to the jib-profiles.js file, which specifies the version of jtreg to use, for those systems that rely on this file. In addition, the `requiredVersion` has been updated in the various `TEST.ROOT` files.

All the tests that could be updated ahead of time have been updated. There are a few tests remaining that need to be done at this time, because of the change in the module name for TestNG 7.3. It changed from a default of `testng` to and explicit `org.testng`.

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Commit messages:
 - JDK-8266254: Update to use jtreg 6

Changes: https://git.openjdk.java.net/jdk/pull/4315/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4315&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266254
  Stats: 17 lines in 11 files changed: 0 ins; 1 del; 16 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4315.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4315/head:pull/4315

PR: https://git.openjdk.java.net/jdk/pull/4315