Add a new upload source

[joelanford]

Getting a simple source implementation in place to support local bundle content is a major quality of life improvement from the current local source that uses a configmap to store bundle contents. However, this implementation has two major drawbacks:

• It limits the size of a bundle to the maximum etcd value size (minus overhead), which can be as little as 1MB
• It currently only supports plain manifest bundles because configmaps don't directly support directory hierarchies (this could be overcome by switching to a BinaryData tar archive value rather than the current key/value per file format).

To level-up our support for allowing operator authors to reference local bundles on-cluster, I propose a different mechanism: Run an RBAC-protected webservice on-cluster that:

• Accepts PUT requests for non-unpacked bundles with source type binary (name TBD).
• Accepts GET requests so that bundle provisioners can fetch the uploaded content.

This mechanism would solve both of the main drawbacks of the existing local source type.