feat: add --skip-snapshot arg which skips all build snapshots

[Owez]

Fixes #1615

Description

This PR adds a new --skip-snapshot argument which skips running any snapshots at all. Right now people run --single-snapshot for performance reasons, but an edge case is not taking any snapshots at all.

Two asterisks to this contrib:

• I don't know much Go so I'm not sure where/how to add unit tests sorry.
• I had a look through build() and I believe snapshots/cache are uploaded as and when rather than having any further processing, so not having any snapshots should be alright?

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you review them:

• [ ] Includes unit tests
• [ ] Adds integration tests if needed.

Reviewer Notes

• [ ] The code flow looks good.
• [ ] Unit tests and or integration tests added.

Release Notes

Describe any changes here so maintainer can include it in the release notes, or delete this block.

- kaniko adds a new --skip-snapshot argument which skips taking any snapshots

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