* Move description and ingroup annotations from PHP file docblock to
class docblock, where IDEs and Doxygen (and humans!) tend to read it
from.
This is in part evidences by the fact that for numerous classes,
the file docblock was copy-pasted and actually about a different
class.
Follows-up Ia3b9b8c22 (page), I301f471f86 (language),
I216d85c6df (PageEditStash), and others that apply similar doc
improvements.
* Add missing `@defgroup` for page. Without this, the group is ignored
and not added in the sidebar at
<https://doc.wikimedia.org/mediawiki-core/master/php/>
* Clean up the file header, similar to other commits under
<https://gerrit.wikimedia.org/r/q/message:ingroup+owner:Krinkle>.
Change-Id: I94de8299c184fee8c05b7108448255fcf36f8260
Exceptions classes are nearly always value objects, and should in most
cases by newable.
Bug: T247862
Change-Id: I4faa8ec6ea8bc44086cfc8075b32d10eea61e9df
