RFR: 8361950: Update to use jtreg 8 [v6]

[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:

  Fix copyright header
  
  [skip ci]

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26261/files
  - new: https://git.openjdk.org/jdk/pull/26261/files/7f2017b4..fd7bf6fd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26261&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26261&range=04-05

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 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