R1:dff028c4907d

Update PonderQuestion for Modular Transactions

Summary: Ref T12624, this moves PonderQuestion over to modular transactions.

Test Plan:
- Create a question
- Edit a question
- Comment on question
- Answer question
- Edit Answer
- Close Question
- Verify answer count in list views
- Check Question History
- Check Answer History

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12624

Differential Revision: https://secure.phabricator.com/D17810