Remove k8schain, directly depend on cred helpers

[imjasonh]

This bumps to the latest k8schain dep, but then removes it entirely, instead preferring to replace NewNoClient with the equivalent cred helper wrappers without the (unused) keychain that used Kubernetes secrets.

Since these were unused, this should not be a functional change, and now we can drop the large k8s.io client dependencies. 🎉

Closes #1872

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Remove cred helpers from images. Instead, we statically link the same cred helper logic into kaniko.

[mattmoor]

🤩

[mattmoor]

Other than figuring out the release orchestration, this seems like a great change.

I see unit tests failing, and think we should discuss the release bits, but otherwise this LGTM.

[imjasonh]

🤩

🤩🤩