Rename wildfly-test-galleon-pack to wildfly-test-feature-pack

The pattern of calling feature packs 'galleon packs' is a leftover from years ago when we were translating from a previous build tech that used the term 'feature pack'. So things were called 'galleon packs' to avoid conflicts.

Those days are long behind, and the Galleon documentation plus any configuration settings in tooling that uses Galleon all call these things 'feature packs'. So we should too.

This is an incompatible change for the primary FPs out there, but it's not for wildfly-test-galleon-pack, which is a purely internal thing.