Move Files to ModularTransactions

Summary: Ref T11357. A lot of file creation doesn't go through transactions, so we only actually have one real transaction type: editing a file name.

Test Plan:
Created and edited files.

{F4559287}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11357

Differential Revision: https://secure.phabricator.com/D17610