[Thinkit] Add SSH Client support to NSF Upgrade test skeleton infrastructure.Implement NSF test utils which is used by NSF Upgrade test.Remove dummy Replay flow programmer.Add Mirror testbed variant along with Generic testbed support to Pushpins NSF test infra.

[Thinkit] Add SSH Client support to NSF Upgrade test skeleton infrastructure.Implement NSF test utils which is used by NSF Upgrade test.Remove dummy Replay flow programmer.Add Mirror testbed variant along with Generic testbed support to Pushpins NSF test infra. #4522