Motivation:
* Remove need to hardcode out-of-component files in various places.
Especially for Gerrit queries, this not only reduces effort but
also makes these files more likely to show up in the first place.
* Clarify component boundaries and ownership, e.g. when filing tasks
with a stack trace.
* Now rather than later, to avoid need for multiple class renames and
aliases when PSR-4 namespaces are applied later (T166010).
Background:
Similar to how jobs in extensions belong to that extension, the same
is true within core. There is a distinction between the JobQueue system,
and individual jobs belonging to a specific feature or component,
likewise for deferred updates, and special pages.
To make a begin with this, I propose moving the job classes to their
respective components for cases where component boundaries are already
clear. E.g. due to exclusively being queued by that same component,
being named/introduced by the same commit, being already documented
as such in component descriptions on mediawiki.org.
Bug: T364652
Change-Id: I73d6b97c6ca9f5abd29f4277d0f845426aa23bd0
b432fd2f20