In Harbormaster, make sure artifacts are destroyed even if a build is aborted

Summary:
Ref T9252. Currently, Harbormaster and Drydock work like this in some cases:

1. Queue a lease for activation.
2. Then, a little later, save the lease PHID somewhere.
3. When the target/resource is destroyed, destroy the lease.

However, something can happen between (1) and (2). In Drydock this window is very short and the "something" would have to be a lighting strike or something similar, but in Harbormaster we wait until the resource activates to do (2) so the window can be many minutes long. In particular, a user can use "Abort Build" during those many minutes.

If they do, the target is destroyed but it doesn't yet have a record of the artifact, so the artifact isn't cleaned up.

Make these things work like this instead:

1. Create a new lease and pre-generate a PHID for it.
2. Save that PHID as something that needs to be cleaned up.
3. Queue the lease for activation.
4. When the target/resource is destroyed, destroy the lease if it exists.

This makes sure there's no step in the process where we might lose track of a lease/resource.

Also, clean up and standardize some other stuff I hit.

Test Plan:

• Stopped daemons.
• Restarted a build in Harbormaster.
• Stepped through the build one stage at a time using bin/worker execute ....
• After the lease was queued, but before it activated, aborted the build.
• Processed the Harbormaster side of things only.
• Saw the lease get destroyed properly.

Reviewers: chad, hach-que

Reviewed By: hach-que

Maniphest Tasks: T9252

Differential Revision: https://secure.phabricator.com/D14234