build(gradle): update Gradle and dependencies

[soloturn]

To prepare for upgrading to newer Java versions and generally keep the launcher's dependencies up-to-date this PR does

• fix the Artifactory URL
• update Gradle 8.8
• update build jobs to use Java 17
• update dependencies

[BenjaminAmos]

This is a logical first step, however, it will break running older releases with these changes. The launcher will need the ability to launch the game using multiple different JREs to keep those older builds functional. From my perspective, that can be implemented separately from this change.

For this pull request though, the only changes I require are to use Java 17 JREs instead of Java 21 ones. Although I've tried to keep Java 21 working, we're not supporting it officially yet and we don't test it much during development.

[skaldarnar]

If I see this correctly this is just upgrading Gradle and dependencies, and using Java 17 (which should all still be fine for the older games, right?).

So, let's get this merged, and let's try to make the launcher actively handle JREs for the games to (as previous PRs already prepared for that).

done