Resolve "Implement gNMI subscription management"

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Related to #382

controller/northbound/server/submanagement.go

@@ -27,8 +27,7 @@ func (s *SubManagementServer) ResetAllSubscriptions(ctx context.Context, request
 
 	s.networkElementWatchter.StopAndRemoveAllNetworkElementSubscriptions()
 
-	// Requires some rework of current way how paths/options are provided to the watcher.
-	s.networkElementWatchter.SubscribeToNetworkElements(subscriptions[0].Opts)
+	s.networkElementWatchter.SubscribeToNetworkElements(subscriptions)
 
 	return &subpb.ResetAllSubscriptionsResponse{
 		Timestamp: time.Now().UnixNano(),
@@ -42,7 +41,6 @@ func (s *SubManagementServer) GetAll(ctx context.Context, request *subpb.GetAllR
 	subInfosToReturn := make([]*subpb.Subscription, 0)
 
 	for _, info := range subInfos {
-
 		tmpPaths := make([]*subpb.Path, 0)
 		for _, path := range info.Opts.Paths {
 			tmpPaths = append(tmpPaths, &subpb.Path{