[v2] Add additional logic to catch potential issues with users using image defaults that don't correspond to the image names in the build.artifacts[].image

[aaron-prindle]

Related to https://github.com/GoogleContainerTools/skaffold/issues/6952

This issue tracks adding additional logic to upgrade.go for v2beta29 to aid users in catching any errors related to them using image defaults that don't correspond to the image names in the build.artifacts[].image and so their deployments may cease to work. The idea would be to do something like:

• use helm template and then read the rendered manifest
• see if there are any image: in the rendered manifest
• see if there are any images skaffold built that aren't used in the manifest
• perhaps also see if there are any empty image: fields? (values that were empty or possibly misconfigured which will break a deployment)

and error (or warn but most likely error) to alert users of possible issues

EDIT: Talked with @briandealwis offline who originally thought of adding this functionality, this would be a feature to help users and is not specifically related to upgrading or potential regressions from v2beta29 -> v3alpha1. This is just to help users that currently use the incorrect image tags in their helm charts