When loading services by class loader (`ServiceLoader.load(Class,ClassLoader)`), the module layers bound to the given class loader are searched for services, along with the layers bound to class loader's parent, and so on. For non-hierarchical class loader arrangements, this breaks down because the parent class loader of non-hierarchical class loaders is typically `null` (i.e. the boot class loader), while the class loader might have multiple dependency class loaders which replace the role of parent.

Add an API to `ClassLoader` which allows additional layers to be bound to the class loader for the purpose of service loading by class loader, without affecting reliable configuration of modules (see JDK-8346439), which allows non-hierarchical class loaders to resolve service providers in dependency class loaders.