Upgrade to Gradle 9 for JDK 25 support, remove JDK 11 support

[dehall]

This PR bumps the Gradle version to the latest as of today, 9.2.1, to enable support for JDK 25, the most recent LTS version of Java. Unfortunately this version of Gradle no longer supports JDK 11, so our new minimum will have to be JDK 17.

One group of dependencies needed to be updated to work with JDK 25 (GraalVM, which powers the JavaScript engine that runs Graphviz and one of the Flexporter actions) but other than that everything should work as is. Many thanks to those who upgraded the build.gradle file already to get it compatible with Gradle 9 for making this easy.

Addresses #1636 .

[jawalonoski]

Checked out and tested. Works as advertised.

I think we should wait to merge for the Synthea major version change as discussed elsewhere.

I noticed there are also gradle deprecation warnings in ./build/reports/problems/problem-report.html... It wasn't clear how much effort it would take to address these warnings.

[dehall]

One of the 4 new deprecation warnings is trivial to fix so I pushed that up.
The rest are on the 3 lines in this section, apparently "archives" is deprecated:

artifacts {
    archives jar
    archives sourceJar
    archives javadocJar
}

It seems like there should be a straightforward replacement for this ( https://docs.gradle.org/9.2.1/userguide/upgrading_version_9.html#archives-configuration ) but I'm not immediately sure of all of the implications, especially for things like maven publishing. I'll keep looking as time permits