An HTTPAcceptor brings some config and classloading deps that can probably be better controlled if a capability were used.

1) Once WFCORE-4166 is done a capability requirement can be used for the required HttpListenerRegistryService, which will help ensure config consistency by making the config links clear.

2) If there are any module dependencies the messaging subsystem module has that are only needed to support an HTTPAcceptor, then those can be made optional, and then the RuntimeCapability.Builder.addAdditionalRequiredPackages method can be used to record the requirement for those optional packages if the new capability is present. (Actually, at a glance it looks like the relevant module deps are already optional, so this bit is about telling Galleon when they are required.)