Basic automated testing

[maths22]

Adds simple integration tests that run javapackager on a simple application and then install and run the package that was created

Currently macos only. Will try to add windows and linux soon

[fvarrui]

Hi Jacob! Sorry this sat for so long. While preparing 2.0.0 we ended up doing most of it on devel without noticing this draft:

• The native macOS launcher is the default (macStartup=UNIVERSAL, ADR-002).
• The deprecated Gradle APIs are gone (Gradle 9 ready, launch4j Gradle plugin 4.0.0).
• .github/workflows/smoke-tests.yml packages samples/hello-world (one sample with both pom.xml and build.gradle) on every push, on GNU/Linux, Windows and macOS (every macStartup, Maven and Gradle), and runs the app checking its output, appArgs and vmArgs.

What your test had and ours didn't was installing the app like a user. I've ported that idea in 168e68c, with you as co-author: check-macos-app.sh now copies the app from the DMG to /Applications, installs the PKG with installer (moving the built bundle aside, as you found), and opens it through Launch Services with open --stdout, so the output can be checked without changing the app.

devel also moved to the io.github.javapackager packages, so this branch doesn't apply anymore. Would you close it, or tell me if there's something here I missed that you'd like to keep?

[maths22]

I don't think there's anything else from this one. I left it as a draft because I never got around to the windows and Linux parts of it.