RFR: 8369488: Update to use jtreg 8.1

[Iris Clark]

On Thu, 9 Oct 2025 09:34:11 GMT, Christian Stein <cstein at openjdk.org> wrote:

> Please review the change to update to using jtreg `8.1`.
> 
> 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.

Marked as reviewed by iris (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27719#pullrequestreview-3319601046