kustomize-set-image improvements

[Brightside56]

Checklist

• [x] I've searched the issue queue to verify this is not a duplicate feature request.
• [x] I've pasted the output of kargo version, if applicable.
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Proposed Feature

kustomize-set-image promotion step requires setting images[].image field. Proposed feature is to make field non-required

Motivation

Requirement to additionally enumerate images for setting in manifests makes templating of promotionTemplate non-trivial in some cases (where I would like to set all images from freight allowed by requestedFreight).

When unneeded - I wouldn't like my Kargo pipeline to be much aware of how images should be set Instead I would like to avoid complex templating or offload this logic into repository with manifests where possible (and have something like render: {}

Suggested Implementation

• When images[].image field isn't set - kustomize could set all images originating from freight
• There could be a step which allows kustomize build (with Helm plugin) and set images using kustomize.yaml at same time

[krancour]

I am neutral on this... I can 💯 see the convenience of this, but I also have a concern about whether making the behavior deviate much from the actual kustomize edit set image command won't prompt some level of confusion.

Interested in @hiddeco's opinion on this one.