* Add spans to show worker_name and job_id
Always show worker_name and job_id when relevant, by creating spans that
live as long as the worker and the job.
* Remove redundant worker names from fn run_worker
Remove the now redundant worker_name tracing, as the information now
lives at the span level
* Use span when spawning new thread
* Instrument more pertinent functions
Move spans to more pertinent functions. Remove more redundant info, and
change worker_name to just worker
* Change tracing subscriber to log path:line_no
Change from logging target (module name usually) to file path and line
number
ac841400ba