Port Streamplace's HSM feature to go-livepeer for improved Orchestrator / Broadcaster security

[Strykar]

Is your feature request related to a problem? Please describe. HSMs help improve security for stakeholders and has already been tested and deployed on Streamplace by Eli. Storing the key on a hardware device prevents key loss / leaks that a traditional OS / filesystem are vulnerable to as the private key never leaves the HSM. See https://www.nitrokey.com/files/doc/Nitrokey_HSM_factsheet.pdf

Describe the solution you'd like Please port the HSM feature from Streamplace to go-livepeer so Orchestrators and Broadcasters may (optionally) use HSM's like Nitrokey to massively improve security of their infrastructure.

Describe alternatives you've considered There are currently none, but this is opt-in so Orch's who do not wish to use an HSM can continue as-is.

Additional context Many Orchestrators may not wish to learn PKCS11 or deal with the cost / complexity of integrating HSMs so this should definitely be optional to use. This was discussed on yesterday's WC call with @iameli who felt it should not be a lot of effort to port it to go-livepeer.