Refactor the ssh communication channels to malke them extensible to other means of tunneling commands into VMs.

Not every environment supports SSH as a way to tunnel commands into a VM/Machine. This feature would be to refactor SSH into a more extensible means of tunneling commands.

Likely the design would be;
- Create a base transport class with send command, send_and_wait for command, etc. We have a number of variants on RemoteCommand today.
- Extend the base transport to have an SSH/RDP/... specialization.
- Specializations can include parameters in the config file
- When the benchmarker starts it can default to the needed transport as part of config.
- The transport class should be a member of the VM vs being global like SSH is today. The would allow for different transports when benchmarking cross environments.