add option to generate override values.yaml based on data passed into skaffold.yaml

[louis-murray]

This is the implementation for #585.

When looking at the code more I saw the reason that values only contains images so I made a new field called overrides that will contain the contents of the generated override values.yaml.

I think the best course of action to clear up any confusion would be to rename the values section to something more image related like artifacts and then the overrides section I've implemented here would become values. I'd be happy to include that change in this PR but didn't want to introduce a breaking change without speaking about it first. Otherwise, it's just something to keep note of for the next major version bump

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[louis-murray]

I signed it!

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CLAs look good, thanks!

[dgageot]

@louis-murray Can you please rebase?

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[louis-murray]

@dgageot done!

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CLAs look good, thanks!

[r2d4]

Thanks!