Add admin API to send trace notifications to registered (#7128)

Remove current functionality to log trace to file
using MINIO_HTTP_TRACE env, and replace it with
mc admin trace command on mc client.

cmd/gateway-main.go

@@ -158,6 +158,9 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 		registerSTSRouter(router)
 	}
 
+	// initialize globalTrace system
+	globalTrace = NewTraceSys(context.Background(), globalEndpoints)
+
 	enableConfigOps := globalEtcdClient != nil && gatewayName == "nas"
 	enableIAMOps := globalEtcdClient != nil