debug: tool to check for DNS resolution from meshed Pod

[draychev]

Augment tests to first perform a DNS lookup (nslookup, dig) for the service a client needs. For example dig bookstore.bookstore

This guarantees that required service has been registered with the Kubernetes DNS.

This check needs to happen after a Service has been created and before the e2e tests log-into the pod and run the test commands.
For example: https://github.com/openservicemesh/osm/blob/release-v0.8/tests/e2e/e2e_tcp_client_server_test.go#L71

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Similar task: #2728

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Update: let's introduce this new functionality in a new pkg/troubleshoot (name TBD). From that package we can use it in e2e or any tests. This new package should also eventually become a CLI for troubleshooting OSM.

[shashankram]

We haven't seen a need to integrate DNS lookups in test. The existing logic has been working well lately. Closing this for now.