Go: introduce JavaTypeShallowClass

[greg-at-moderne]

What's changed?

In Go, introducing the JavaTypeShallowClass next to the already existing JavaTypeClass.
As a consequence in a lot of places, we need to use FullyQualified super type instead of JavaTypeClass.

What's your motivation?

Without this, the JavaTypeShallowClass objects get conflated/coerced into JavaTypeClass over RPC. And unexpected things happen. The symptoms observed include:

java.lang.IllegalArgumentException: No enum constant org.openrewrite.java.tree.JavaType.FullyQualified.Kind.
  java.base/java.lang.Enum.valueOf(Enum.java:293)
  org.openrewrite.java.tree.JavaType$FullyQualified$Kind.valueOf(JavaType.java:389)
  org.openrewrite.java.internal.rpc.JavaTypeReceiver.lambda$visitClass$7(JavaTypeReceiver.java:74)
  org.openrewrite.rpc.RpcReceiveQueue.receiveAndGet(RpcReceiveQueue.java:71)
  org.openrewrite.java.internal.rpc.JavaTypeReceiver.visitClass(JavaTypeReceiver.java:74)