Kotlin source dir parsing bugfix

[nmck257]

Fix bug where Kotlin test source parsing actually parsed main dir a second time, and test sources were later parsed as additional resources

What's changed?

What's your motivation?

Anything in particular you'd like reviewers to focus on?

Anyone you would like to review specifically?

Have you considered any alternatives or workarounds?

Any additional context

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[timtebeek]

Thanks!