Fix "Blocked" task queries with multiple subtasks, and update language
Summary:
Ref T8126. See that task for discussion. This change:
- Updates language to be more consistent ("Parents", "Subtasks") since I moved us away from the often-confusing "Block" language in T4788.
- Fixes bugs with finding the wrong set of tasks if tasks have a mixture of open and closed subtasks or parents.
Test Plan:
- Created four tasks: no subtasks, one closed subtask, one open subtask, mixture of open and closed subtasks.
- Created four more tasks: no parents, one closed parent, one open parent, mixture of open and closed parents.
- Searched for all this stuff, got the proper results:
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T8126
Differential Revision: https://secure.phabricator.com/D16340