RFR: 8361950: Update to use jtreg 8 [v3]

[Christian Stein]

> Please review the change to update to using jtreg 8.
> 
> 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.

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 four additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8361950-jtreg-8
 - Update to use correct library directories
   
   See also: https://openjdk.org/jtreg/faq.html#how-do-i-find-the-path-for-the-testng-or-junit-jar-files
 - 8361950: Set required version to 8+2
 - 8361950: Update to use jtreg 8

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26261/files
  - new: https://git.openjdk.org/jdk/pull/26261/files/b5112c32..56006240

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26261&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26261&range=01-02

  Stats: 79727 lines in 2045 files changed: 46139 ins; 24474 del; 9114 mod
  Patch: https://git.openjdk.org/jdk/pull/26261.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26261/head:pull/26261

PR: https://git.openjdk.org/jdk/pull/26261