Ensure JAX-RS usable features don't depend on jaxws

Follow up of https://lists.apache.org/thread.html/c68c4c73b4af274d2f0e162e8b5df62942d8cad41d829a9e2fa7a2f5@%3Cdev.cxf.apache.org%3E discussion.

Idea is to not force JAXRS users to depend on jaxws in terms of dependency. Whereas it was acceptable for java <= 8, it is now impacting in java >= 9 since jaxws is no more part of the JRE.

Proposal is to: drop the WebServiceFeature dependency in the AbstractFeature hierarchy by introducing a CxfBaseFeature keeping backward compatibility, provide native implementations of all feature and replace current implementations by plain delegation to the new one - to ensure existing users still have a functional setup. JAXRS users would use the new class and JAXWS ones can use the new one (probably preferred by javadoc) or the old one for compatibility.