I/O: Improve processing and error handling

[amotl]

Problem

How the I/O subsystem is currently doing its processing is, well, a bit ad hoc, and doesn't provide much guidance when it comes to informing callers about progress/status, and final outcome. /cc @hampsterx

Proposal

I would like to introduce a first-citizen model entity that keeps track of all metadata in a typical I/O conversation in the spirit of a context object, let's just call it JobInfo. That context object would be used to serve multiple purposes:

• Track any job metadata and metrics.
• Emit progress/status information while the job is running.
• Be returned when a job finshes successfully.
• Be slotted into a corresponding first-citizen exception object 1:1 when an error happens during an I/O operation, or used as a callback argument to possible error handling hook functions, see I/O: Unify on_error configuration across Kinesis relay and MongoDB CDC #759.