R1:ece9579d258d

Switch File deletion to use ModularTransactions

Summary: Fixes T12587. Adds a new `PhabricatorFileDeleteTransaction` that enqueues `File` delete tasks.

Test Plan:
- hack `PhabricatorFileQuery` to ignore isDeleted state
- stop daemons
- upload a file, delete it from the UI
- check that the DB has updated isDeleted = 1
- check timeline rendering in `File` detail view
- start daemons
- confirm rows are deleted from DB

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin…