JBangIntegration needs some TLC ASAP

[dmlloyd]

Describe the bug

When trying to update jboss-threads in #43648/#43634 a JBang integration test has started to fail. Long story short, classes from jbang.jar are leaking on to the Quarkus class path somehow. It's likely related to one or more of the various (probably obsolete) class resolution workarounds which can be found in io.quarkus.launcher.JBangIntegration in the core/launcher submodule.

This code needs to be reviewed to see if any of these workarounds are still needed and/or if they are causing issues like the one described above.

Expected behavior

No class path leakage.

Actual behavior

Lots of class path leakage!

How to Reproduce?

No response

Output of uname -a or ver

No response

Output of java -version

No response

Quarkus version or git rev

No response

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response

[quarkus-bot]

/cc @maxandersen (jbang), @quarkusio/devtools (jbang)