Allow registry credentials to be passed into kbld in template

**Describe the problem/challenge you have**
I was looking to have a small App CR that took my main branch from git with k8s YAML in it, run a kbld on it, and deploy it.
It's better to have the sha256 image URLs rather than latest or even me manually editing it for versions.

**Describe the solution you'd like**
- Could just add a secretRef field to the kbld section
- Could allow kbld to re-use secretRefs from the fetch.image and/or fetch.imgpkgBundle
- Have kbld+image+imgpkgBundle all support registry credentials from the serviceAccount

**Anything else you would like to add:**
Relevant Slack thread with a small sample: [https://kubernetes.slack.com/archives/CH8KCCKA5/p1658544850496609](https://kubernetes.slack.com/archives/CH8KCCKA5/p1658544850496609)

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