Add PasswordFactory to MediaWikiServices

Add PasswordFactory to MediaWikiServices

Instead of having basically every caller do:
 $pf = new PasswordFactory();
 $pf->init( RequestContext::getMain()->getConfig() );
Just create a single PasswordFactory via MediaWikiServices and pass that
around. Things that want to use their own config can still pass settings
via the new constructor.

This will eventually let us remove the init() function, removing the
only hard dependency upon MediaWiki, to make it easier to librarize
(T89742).

Change-Id: I0fc7520dc023b11a7fa66083eff7b88ebfe49c7b