Uploading packages should return a Location header with a link to a job resource

Package upload already uses a delayed job to handle the upload:

https://github.com/cloudfoundry/cloud_controller_ng/blob/a07e31411712d3ee196f26032f087ab84949cd53/app/controllers/v3/packages_controller.rb#L63-L68

Clients likely already have mechanisms for polling job resources returned from other async endpoints. It would make their lives easier if the CC returned a Location header pointing to a job resources that they can poll to see when the upload completes (instead of having to write a custom poller for packages). This will also match the proposed behavior for v3 buildpack uploads: https://www.pivotaltracker.com/story/show/162669794

One thing that might complicate this is the Bits Service. If clients are uploading the package directly to the Bits Services, then they will currently not get a job on the CC to poll.

Start with app/controllers/v3/packages_controller.rb at lines 63-68 and trace both the delayed upload path and the direct Bits Service path. Compare how other asynchronous endpoints expose job resources and determine the expected behavior when the Bits Service is involved. Done means package uploads return a usable Location header when a Cloud Controller job exists, with the Bits Service case explicitly handled.