[oe] [meta-java] Unify virtual java providers

[Pascal Bach]

Hello


Because I'm experimenting with different java providers (OpenJDK, Oracle Java, Azul Zulu) and thus had a look at different java layers (meta-java, meta-oracle-java).

I noticed that there are many different PROVIDES statements among these recipes, but nothing seems consistent.

My proposal is thus to introduce a consistent naming for these provides so that recipes that depend on java can be written in a JRE/JDK independent way.
The naming would be the following:

- virtual/java => recipes providing a java runtime for the target (used in meta-oracle-java, replaces: java2-runtime, java2-vm)
- virtual/java-native => provide a native java runtime (exists already)
- virtual/javac => provide a jdk for the target (new, nothing like this exists, might never be used but should be defined)
- virtual/javac-native => provide a jdk for native (exists already)

It should be properly documented in the readme and the virtual packages should be the preferred way for users to depend on java/jre resp javac/jdk

An alternative to the above would be:

- virtual/jre
- virtual/jre-native
- virtual/jdk
- virtual/jdk-native

But this would deviate more from the current naming.

Any feedback on this proposal?

Pascal