[PATCH 2 of 3] configitems: use codemod script to register coreconfigitems

[Jun Wu]

Excerpts from Augie Fackler's message of 2017-07-14 14:39:17 -0400:
> Urg. This is kind of unreviewable, because it's gathering configitems
> from everywhere and splatting them in one big file, so it's hard to
> audit defaults etc.

Why is audit needed if defaults are written by code, not human?

> Could we maybe migrate one file's config items at a time to
> configitems.py? I know it'd be a huge series, but I could rip through
> that extremely quickly via mail, whereas this big hairball is going to
> be very hard to check.

Per file is not a good idea, since if two files have "config('a', 'b',
'c')", they need to be changed in a single patch.