Start running Nitro tests in the CI

[dreemkiller]

Requested feature
Add AWS Nitro enclave tests to our CI

Motivation
Currently, AWS Nitro builds are done in the CI, but nothing is run on the Nitro platform. This means that regressions on Nitro are not found until someone runs them manually.

Additional context
As an example of a regression, #511 discusses RNG issues on Nitro

[gbryant-arm]

We could also deploy VOD on Nitro. Cf. #597

Some ideas:

• how to SSH securely
  • store client's private key & server's IP addr in "github secrets"
  • pin sever's public key somewhere
    in github secrets too? would probably have to poke @dreemkiller every time you change it
• protocol
  • start docker container on remote machine
  • run deployment
  • fetch artifacts and logs from remote machine and propagate error codes