Accessing Process Stats

[hyperthunk]

Leading on from issue 65 comment 2, it would be nice to be able to get some per-process stats, such as message queue length.

Presumably we could look at the map of typed channels stored in the process state to get some useful metrics out of that too. Quite how efficient looking at the types would be I'm not sure, but it does sound useful.

Also, another assumption I'm making here is that this would need to be a primitive.

[hyperthunk]

Initial stab at this here. I have indeed made it a primitive and it is dispatched to, and handled via the target process' node controller. This allows you to get process info for remote processes, which is something erlang's process_info does not.

[hyperthunk]

Looks like we can't get the mailbox size easily without blocking the caller - this can so easily lead to deadlock, I'm loth to do it, so I've taken that lookup out for now and will open a separate issue to address it. https://github.com/hyperthunk/distributed-process/compare/process-info

[hyperthunk]

Merged in #111