ANTLR shading doesn't seem to work properly

[beikov]

See https://github.com/quarkusio/quarkus/issues/9142 which shows the exception that we see in an environment where our ANTLR version is not available. I actually thought we shaded ANTLR already, but seems like I need to investigate a bit further.

[beikov]

After digging into some problems with the Quarkus 3 integration, I figured that the Quarkus classloader loads classes from target/classes for Maven modules of the current reactor. I suppose that the maven shade plugin only transforms the JAR file, so that would explain why we see this error during testing. I suggest we simply bump to the same ANTLR version for now.