Remove package-schema cruft from wildfly-feature-pack-build.xml files

The various wildfly-feature-pack-build.xml files include 'package-schemas' elements. AIUI the children of those elements only need to refer to maven groupId for which that specific feature pack provides artifacts with schemas. It does not need to include groupIds for artifacts from other f-ps that the f-p depends on. The WF galleon plugin itself combines those.

So the task is

1) to clean out cruft, i.e. elements that are related to artifacts from other feature packs. Helps clarify the expected use of these files.

2) Perhaps in the verifier tests for servlet-dist, ee-dist, dist add verification of the presence of 1 schema from each relevant maven groupId. Guard against schemas suddenly not getting picked up.