Request API Change: Add registration_time for nse registration

[denis-tingaikin]

Suggestion

Add registration_time for the network service endpoints.

message NetworkServiceEndpoint {
    string name = 1;
    repeated string network_service_names = 2;
    map<string, NetworkServiceLabels> network_service_labels = 3;
    string url = 4;
    google.protobuf.Timestamp expiration_time = 5;
    google.protobuf.Timestamp initial_registration_time = 6;
}

How it will be used

expiration_time updates by registry by each refresh register.

registration_time will be set once per registration by the registry side.

registration_time can be used for statistics goals and also for identity issues and sorting issues.

Motivation

1. Solves Registry heal works incorrect if NSMgr changes IP address after restart sdk#1079
2. Solves Simultaneous creation of multiple vl3-NSEs cmd-nse-vl3-vpp#3

[denis-tingaikin]

@edwarnicke WDYT?

[edwarnicke]

@denis-tingaikin Might it make more sense to call it initial_registration_time?

[denis-tingaikin]

@edwarnicke I think yes :)

The description is updated.