This is a follow-up to patches 2-6 of:
[PATCH v2 00/11] blockjobs: Fix transactional race condition

That series started trying to refactor blockjobs with the goal of
internalizing BlockJob state as a side effect of having gone through
the effort of figuring out which commands were "safe" to call on
a Job that has no coroutine object.

I've split out the less contentious bits so I can move forward with my
original work of focusing on the transactional race condition in a
different series.

Functionally the biggest difference here is the presence of "internal"
block jobs, which do not emit QMP events or show up in block query
requests. This is done for the sake of replication jobs, which should
not be interfering with the public jobs namespace.

===
v2
===

01:    Cleaned up error message, fixed strcmp oversight, added assert()
02-07: Added R-Bs. (Does everyone else pronounce this as "Arby's" too?)

________________________________________________________________________________

For convenience, this branch is available at:
https://github.com/jnsnow/qemu.git branch job-refactor-pt1
https://github.com/jnsnow/qemu/tree/job-refactor-pt1

This version is tagged job-refactor-pt1-v2:
https://github.com/jnsnow/qemu/releases/tag/job-refactor-pt1-v2