* Fix Java not compiled in kotlin-gradle-plugin Kotlin source set
* Fix the integration tests running under Java 6
* Fix kotlin-gradle-subplugin-example not being installed -- needed
for a test
* Fix Android tests being always excluded
* Move versions out of `build.gradle` (x2) to a common `versions.gradle`
* Move JDK, dist and bootstrap to `commonConfiguration.gradle`
* Build `kotlin-gradle-plugin` with JDK_18
Sergey Igushkin