Abstract the connection interface with ducktape nodes

[imcdo]

Current status

currently ducktape communicates with all its nodes dirrectly via ssh (and scp for file interactions): https://github.com/confluentinc/ducktape/blob/master/ducktape/cluster/remoteaccount.py

Currently we at confluent at least run ducktape in two capacities: locally with docker, and externally with ec2 instances. Ducktape could be made simpler to use in the docker case if we allowed for cluster type implementations to define the connection type. (or just users)

Proposal

have a generic interface for a "remoteaccount" that has just the key aspects that are needed:

• run commands (with and w/o output, streaming)
• transfer files
  then have the default implementation be the current ssh base remote account,
  but also create a docker cluster type, and a docker connection type, that connects dirrectly with the docker command (docker exec -it sh) removing the requirment of ssh here, simplifying the docker connection allowing for users to more easily start up a docker container network, and connect to it.