Spring Migrate CoroutinesUtils from Kotlin to Java

This PR migrates CoroutinesUtils from Kotlin code to Java. The primary benefit of the change is that the Kotlin module is no longer required when working on the Java code in an IDE. This is especially helpful for Eclipse users (like myself and @sbrannen) as we no longer need to install Kotlin tooling.

Comment From: sdeleuze

Ok from my POV when rebased on top of the latest Gradle changes, with extra care in testing snapshots with my Coroutines samples and with Spring Data which makes an extensive usage of Coroutines cc @mp911de.

Comment From: mp911de

Thanks for the ping. We're not using CoroutinesUtils in Spring Data as we have our own Coroutines to Publisher and vice versa translation.

Comment From: sbrannen

This is now in main.

Thanks, @philwebb!