Revise InterfaceRegistry API to support filtering interfaces @ Bind() time.

services/service_manager/manifest.json

 {
   "manifest_version": 1,
   "name": "service:service_manager",
   "display_name": "Service Manager",
   "interface_provider_specs": {
     "service_manager:connector": {
       // NOTE: This manifest is for documentation purposes only. Relevant
       // capability spec is defined inline in the ServiceManager implementation.
       //
       // TODO(rockot): Fix this. We can bake this file into ServiceManager at
       // build time or something. Same with service:catalog.
       "provides": {
         // Clients requesting this class are able to connect to other clients as
         // specific users other than their own.
         "service_manager:user_id": [ ],
         // Clients requesting this class are allowed to register clients for
         // processes they launch themselves.
         "service_manager:client_process": [ ],
         // Clients requesting this class are allowed to connect to other clients
         // in specific process instance groups.
         "service_manager:instance_name": [ ],
         // Clients requesting this class are run as a unique user id which is
         // visible to clients run as any user.
         "service_manager:all_users": [ ],
         "service_manager:block_wildcard": [ ],
-        // Clients requesting this class block inbound requests to bind interfaces
-        // from other sources who specify wildcard rules in their manifest
-        // capability interface sets.
-        "service_manager:explicit_class": [ ],
 
         "service_manager:service_manager": [
           "service_manager::mojom::ServiceManager"
         ]
       },
       "requires": {
         "*": [ "service_manager:service_factory" ],
         "service:catalog": [ "service_manager:resolver" ],
         "service:tracing": [ "app" ]
       }
     }
   }
 }