Provide an archetype for WildFly feature packs

[jmesnil]

Feature packs (sometimes referred to as Galleon packs) provide the ability to extend WildFly feature without being part of WildFly codebase directly.

It's already used extensively to extend WildFly capabilities (AI, cloud, gRPC, Keycloak, etc.).
However it is non trivial to start a feature pack from scratch.

We could help developers bootstrap new feature packs by providing a new archetype or extending the subsystem archetype so that it also provides a feature pack to provision the minimal subsystem.

[jmesnil]

There is an existing template at https://github.com/wildfly/wildfly-feature-pack-template that is out of date and could be retrofit into an archetype if that makes sense