[Spike]: Implement buildpack management endpoints for buildpacks

[georgethebeatle]

Background

As of today only listing of buildpacks is implemented. Let's look into what it would mean to implement the rest of the endpoints. The goal is to cover the following commands:

   buildpacks                             List all buildpacks
   create-buildpack                       Create a buildpack
   update-buildpack                       Update a buildpack
   delete-buildpack                       Delete a buildpack

Spike outcome

• Detailed stories for creating, updating and deleting of buildpacks
• (Optinal) Proposal document for supporting buildpacks (if we feel that the matter is untrivial and we need some input/comments from the community)

[benjaminguttmann-avtq]

Wouldn't it be possible to implement the create-buildpack as it is described in here => #3598 . To patch the kpack resources to introduce the new buildpack? If yes, I would like to try if I can make that happen