Updated versions / minor cleanup flagged by ktlint

[psh]

I added a version catalog for the project and updated to -

• Kotlin 1.9.23
• Ktlint 12.1.0
• Guava 33.0.0-jre
• Kotest 5.8.1
• Gradle 8.5

Ktlint flagged a couple of things, there were some outdated "experimental" annotations and unused imports.