Investigate converting connection / request-on-conn fibers to use Tasks

[gavin-norman-sociomantic]

It's unfortunate that the task system in ocean came along after we'd already done a significant amount of work on swarm neo, but we should certainly aim to convert it, in the long run.

[gavin-norman-sociomantic]

We'd want a 1:1 ratio of such tasks to worker fibers, but using the same, familiar Task API would be very beneficial for maintenance.