Have the feature pack 'source modules' produce zip artifacts

Follow-up to WFCORE-4993.  Have the new core-feature-pack/common and core-feature-pack/ee-8-api maven modules produce zip artifacts in addition to poms. Convert the core-feature-pack/galleon-common directory into a module that produces a zip as well.

Having these available from a core beta release will allow dev work in full WF to consume them in the WF feature packs, instead of having to depend on the wildfly-core feature pack itself.

See https://lists.jboss.org/pipermail/wildfly-dev/2020-June/007342.html for background.