scala.jdk.javaapi.CollectionConverters for Scala 2.11/2.12

[ijuma]

JavaConverters has been deprecated in Scala 2.13 and the implementation of scala.jdk.CollectionConverters in this library doesn't work well from Java. Implementing scala.jdk.javaapi.CollectionConverters would mean that Java code can move away from the deprecated JavaConverters while supporting Scala 2.11, 2.12 and 2.13.

[ekrich]

I guess that would have to be a JVM only artifact?

[DieBauer]

@SethTisue can this be closed with #551 ?