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

src/applications/transactions/editengine/PhabricatorEditEngine.php

@@ -1676,6 +1676,7 @@ abstract class PhabricatorEditEngine
       ->setUser($viewer)
       ->setHeaderText($header_text)
       ->setAction($comment_uri)
+      ->setRequestURI(new PhutilURI($this->getObjectViewURI($object)))
       ->setRequiresMFA($requires_mfa)
       ->setObject($object)
       ->setEditEngine($this)