Provide authorization to kbld templating step

[ewrenn8]

Describe the problem/challenge you have When using an internal private registry, kbld is unable to authorize in order to resolve image digests.

Describe the solution you'd like A way to provide authorization to the kbld templating step, similar to the various fetch stages.

[aaronshurley]

Recommend doing some research and getting some early feedback on how we should format these propterites.