Consolidate the buildpacks package into a single Client

Consolidate the buildpacks package into a single Client: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Looking at pkg/kf/buildpacks/ , we currently expose three separate interfaces, each with its own constructor, its own implementation file, and its own generated…