For the classes I implemented in the executor/ folder, I qualified them with the namespaces `executor` and `remote_command_runner`. However, for the classes I implemented outside of the `executor/` folder, I just qualified them with the `remote_command_runner` namespace. This is confusing the compiler, and so we need to brainstorm and implement a general solution to the namespaces for this API.

Broadening the scope of this ticket a bit - we'll now 

-> replace all uses of executor::remote_command_runner and remote_command_runner with the single async_rpc namespace

-> Change the naming of the public API and all public types to match