feat(helm): create versioning as proxy of npm

[secustor]

Changes:

Add a helm versioning implementation as proxy to npm as it has a subset of its capabilities.

Context:

This is the result from a discussion in the RenovateBot Slack workspace.

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[rarkins]

@secustor were you planning further work after this? I don't see what difference this practically makes until at least one of the functions differs from npm's implementation.

[secustor]

Not at the moment.
They simply differ in the testcases. As helm supports a subset of npm options.

If there are more differences surfacing like npm changing its behavior. We have an API to change without breaking the user configs.
Further I think it is more straight forward to users to use helm versioning for helm than npm

[renovate-release]

🎉 This PR is included in version 28.4.0 🎉

The release is available on:

• GitHub release
• 28.4.0

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