Replace some manual class name strings with ::class keyword master
Summary: Replace classname strings in `PhabricatorApplicationQuery->withClasses()` call parameter with the corresponding `::class` keyword. This will enable static code analysis to throw "Class not found" if such a class did not exist. `::class` is available since PHP 5.5: https://www.php.net/manual/en/language.oop5.basic.php#language.oop5.basic.class.class `::class` returns the fully qualified classname including namespace, however we do not use PHP namespaces except in imported external libraries. Refs T15158 Test Plan: Browse random Phorge pages? Reviewers: O1 Blessed Committers, mainframe98 Reviewed By: O1 Blessed Committers, mainframe98 Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno Maniphest Tasks: T15158 Differential Revision: https://we.phorge.it/D26347