WFLY-1812 Web session clustering should not require a RegistryService if sessions aren't being replicated.
Refactor wildfly-clustering-registry and wildfly-clustering-singleton into wildfly-clustering-api and wildfly-clustering-server.
Create builder API for singleton services.
Add CacheServiceProvider as cache-view analog to ChannelDependentServiceProvider
Refactor ServiceProviderRegistration to install per cache instead of per channel.
Add Group service to wildfly-clustering-api, with service implementations for both channel and cache.