feat: refactor service list and detail APIs to use serviceName:version:group identity (#1430)

- Change Service proto: remove providers/consumers/features, add methods field
- Service List API: query Service resource instead of ServiceProviderMetadata,
  return serviceName/version/group/serviceKey (no providerAppName)
- Service Detail API: return language + methods from Service resource
- Provider subscriber: sync methods from ServiceProviderMetadata events into
  Service resource (merge/dedup across multiple providers)
- Consumer subscriber: no longer writes to Service resource
- Distribution API: revert to querying ServiceConsumerMetadata index
- Add ByServiceConsumerServiceKey/ByServiceProviderServiceKey indexes
- Frontend: update search/detail/distribution views accordingly
- Add unit tests for service API and subscriber lifecycle

Fixes #1430

Author: mochengqian

api/mesh/v1alpha1/service.pb.go

@@ -21,9 +21,5 @@ message Service{
 
   string language = 4;
 
-  repeated string providers = 5;
-
-  repeated string consumers = 6;
-
-  map<string, string> features = 99;
-}
+  repeated string methods = 5;
+}