Redirect back to object after clicking "Log In to Comment" and login

Summary:
PhabricatorApplicationTransactionCommentView performs $uri = id(new PhutilURI('/login/'))->replaceQueryParam('next', (string)$this->getRequestURI()) but the constructor call in PhabricatorEditEngine does not set any RequestURI so the Log In to Comment button at the bottom of an object view does not redirect back to the object URI after login.

Thus pass a RequestURI to PhabricatorApplicationTransactionCommentView in the constructor call in PhabricatorEditEngine.

Closes T15837

Test Plan: As a Phorge admin, set policy.allow-public to true and create a Maniphest task with Public view policy. As an anonymous user, visit the task and click the Log In to Comment button at the bottom of the single task view, log in, and see that you get redirected to the task.

Reviewers: O1 Blessed Committers, avivey

Reviewed By: O1 Blessed Committers, avivey

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15837

Differential Revision: https://we.phorge.it/D25667