zebra: add dynamic nhg-count field into json output

Currently,  nexthop-group JSON doesn’t have the field to show the dynamic
nexthop group count.

Fix:

Added nhg_count field to provide the dynamic nexthop grp count info.

supported commands:

```
show nexthop-group rib brief json
show nexthop-group rib json
```

Ticket:#3963582

Issue:3963582

Signed-off-by: Sindhu Parvathi Gopinathan's <sgopinathan@nvidia.com>

Author: Sindhu Parvathi Gopinathan

zebra/zebra_vty.c

@@ -1501,6 +1501,7 @@ struct nhe_show_context {
 	int type;
 	json_object *json;
 	bool brief;
+	uint32_t nhg_count;
 };
 
 static int nhe_show_walker(struct hash_bucket *bucket, void *arg)
@@ -1520,13 +1521,14 @@ static int nhe_show_walker(struct hash_bucket *bucket, void *arg)
 		goto done;
 
 	show_nexthop_group_out(ctx->vty, nhe, ctx->json, ctx->brief);
+	ctx->nhg_count++;
 
 done:
 	return HASHWALK_CONTINUE;
 }
 
 static void show_nexthop_group_cmd_helper(struct vty *vty, struct zebra_vrf *zvrf, afi_t afi,
-					  int type, json_object *json, bool brief)
+					  int type, json_object *json, bool brief, uint32_t *nhg_count)
 {
 	struct nhe_show_context ctx;
 
@@ -1536,8 +1538,10 @@ static void show_nexthop_group_cmd_helper(struct vty *vty, struct zebra_vrf *zvr
 	ctx.type = type;
 	ctx.json = json;
 	ctx.brief = brief;
+	ctx.nhg_count = 0;
 
 	hash_walk(zrouter.nhgs_id, nhe_show_walker, &ctx);
+	*nhg_count = ctx.nhg_count;
 }
 
 static void if_nexthop_group_dump_vty(struct vty *vty, struct interface *ifp)
@@ -1609,6 +1613,7 @@ DEFPY(show_nexthop_group, show_nexthop_group_cmd,
 	bool uj = use_json(argc, argv);
 	json_object *json = NULL;
 	json_object *json_vrf = NULL;
+	uint32_t nhg_count = 0;
 
 	if (uj)
 		json = json_object_new_object();
@@ -1652,10 +1657,13 @@ DEFPY(show_nexthop_group, show_nexthop_group_cmd,
 			else
 				vty_out(vty, "VRF: %s\n", vrf->name);
 
-			show_nexthop_group_cmd_helper(vty, zvrf, afi, type, json_vrf, brief);
-			if (uj)
+			show_nexthop_group_cmd_helper(vty, zvrf, afi, type, json_vrf, brief, &nhg_count);
+			if (uj) {
+				json_object_int_add(json, "nhgCount",
+						    nhg_count);
 				json_object_object_add(json, vrf->name,
 						       json_vrf);
+			}
 		}
 
 		if (uj)
@@ -1678,9 +1686,11 @@ DEFPY(show_nexthop_group, show_nexthop_group_cmd,
 		return CMD_WARNING;
 	}
 
-	show_nexthop_group_cmd_helper(vty, zvrf, afi, type, json, brief);
+	show_nexthop_group_cmd_helper(vty, zvrf, afi, type, json, brief,
+				      &nhg_count);
 
 	if (uj) {
+		json_object_int_add(json, "nhgCount", nhg_count);
 		if (brief)
 			vty_json_no_pretty(vty, json);
 		else