pull command should indicate why images.yml was not localized

**Describe the problem/challenge you have**
currently imgpkg just says images.yml was not localized. it's not clear _why_ it was not -- we should probably include underlying error/reason and related image. probably should give a reason even if it was successful.

this would have been handy when we were trying to figure out why images.yml was not coming back rewritten after imgpkg copy used (problem was some images were returning denied).

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Trace the pull command's images.yml localization reporting and reproduce the case where an image is denied during imgpkg copy. The work is done when the command reports why localization was skipped, identifies the related image, and gives a reason when localization succeeds.

Written by the indexing model from the issue text.