RFR: 7904062: Release jtreg 8

[Iris Clark]

On Thu, 10 Jul 2025 15:18:42 GMT, Christian Stein <cstein at openjdk.org> wrote:

> Please review this change preparing the release of jtreg 8.
> 
> This commit only updates the `CHANGELOG.md` file to include
> a selected set of noteworthy changes under the new *8* section.
> 
> The `make/build-support/version-numbers` file is already good
> to go for the initial 8.x release.

Marked as reviewed by iris (Reviewer).

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PR Review: https://git.openjdk.org/jtreg/pull/273#pullrequestreview-3006253051