Gradle with IntelliJ IDEA does not recognise Java and Kotlin source and TestNG tests

1. Changing id 'org.jetbrains.kotlin.multiplatform' version "$kotlin_version" to id 'org.jetbrains.kotlin.jvm' version "$kotlin_version" and
2. removing

kotlin {
    jvm {
        withJava()
    }
}

solves all 3 problems.