Consider moving Kotlin examples to their own package

[snicoll]

With the move to Kotlin 2, the compiler forbids the use of a Java class and a Kotlin class with the same FQN. We've temporarily removed java source code from the kotlin compilation to work around this but we should probably offer a better option

spring-boot/spring-boot-project/spring-boot-docs/build.gradle

Lines 66 to 69 in 669e4cd

	// To avoid a redeclaration error with Kotlin compiler
	tasks.named('compileKotlin', KotlinCompilationTask.class) {
	javaSources.from = []
	}