Support KSP for writing extensions in Kotlin

[Tanemahuta]

Description

Background:

• kotlin is a popular language (rightly so)
• kapt is the adapter for java annotation processing
  • the is in maintenance mode
  • does not support kotlin 2
• ksp is the replacement for kapt
  • works different
  • does not support the java annotation processing
  • more efficient

I (and probably not only me) would love to see support for KSP for the quarkus-extension-processor. I'd be willing to help with the modifications.

Implementation ideas

• modify the interface for io.quarkus.annotation.processor.ExtensionProcessor:
  • introduce an abstraction for javax.annotation.processing.RoundEnvironment and javax.lang.model.element.TypeElement
• adapt the broken code
• extract all generic code to a new library, which has no dependency on the annotation processor
• create a new module for java annotation processing
• create a new module for ksp and implement the code

[quarkus-bot[bot]]

/cc @geoand (kotlin)

[kdubb]

We use Kotlin and have local extensions that we wrote in our Gradle build... and we ran into another issue, you need to output all your Kotlin code to src/main/java (in Gradle we renamed it to Kotlin but the built classes dir had to stay java).