RFR: 8361950: Update to use jtreg 8 [v2]

[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 incrementally with one additional commit since the last revision:

  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

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26261/files
  - new: https://git.openjdk.org/jdk/pull/26261/files/bf7b033b..b5112c32

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26261&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26261&range=00-01

  Stats: 30 lines in 2 files changed: 8 ins; 19 del; 3 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