Build offline cnb builder
Build offline cnb builder

- Use github.com/pivotal-cf/p-cnb-builder for builder config
- Increase fixtures used in smoke-test
- rename cnb-builder jobs
- Only trigger builder rc jobs on cnb releases to not
  add too many builder rcs to our remote repos

[#165834607]

Co-authored-by: Chhavi Kankaria <a45f933d80ef78816bcf302f872972e3887e5115@pivotal.io>

cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci