R1:064424c1b755

Add getQueryApplicationClass() to *TransactionQuery.php classes

Summary:
Add `getQueryApplicationClass()` to all `*TransactionQuery.php` classes similar to other `*Query.php` classes having the same function, and make the parent function in `PhabricatorApplicationTransactionQuery.php` abstract.

In the future, this will enable excluding transaction query results based on their underlying application (for example if an application has been uninstalled) to mitigate the problem of overheated search results.