R1:3215899925e2

Execute Maniphest batch edits in the background with a web UI progress bar

Summary:
Ref T8637. This does nothing interesting, just has empty scaffolding for a bulk job queue.

Basic idea is that when you do something like a batch edit in Maniphest, we:

- Create a BulkJob with all the details.
- Queue a worker to start the job.
- Send you to a progress bar page for the job.

In the background:

- The "start job" worker creates a ton of Task objects, then queues worker tasks to do the work.

In the…