docs(customresourcestate): add example to expose same metrics with different label

[clavinjune]

What this PR does / why we need it: Give an example on how to expose a same metrics with different label (VPA recommendation for example)

How does this change affect the cardinality of KSM: does not change cardinality directly since this is an optional / custom resource state metrics

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

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• ✅ login: clavinjune / name: Clavianus Juneardo (a4d64fb, 1412eaa, 89f8110, 387bd8b, ae38bc4)

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[clavinjune]

should I create docs to cover #2041? cc @QuentinBisson

[QuentinBisson]

@clavinjune that would be amazing :)

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[clavinjune]

added here @QuentinBisson @CatherineF-dev @logicalhan

[QuentinBisson]

Amazing thank you 🚀

[CatherineF-dev]

Try to make metric name shorter if it's possible

For example, vpa_policies_minallowed

[clavinjune]

I'm trying to make it the same as the previous metrics which are removed, so I made it the same. If we changed the metrics name here, it defeats the purpose to re-expose the removed metrics. The plan is to have no parity between the metrics removed with this guide. wdyt @CatherineF-dev?

[rexagod]

Inferring the naming based on the Prometheus conventions, and as such, for instance, and taking into consideration Catherine's comment, this may be changed to:

vpa_spec_resourcepolicy_container_policies_minallowed_bytes

However, since the point is to polyfill these metrics, it makes sense to not break the previous names.

[rexagod]

I believe it somehow slipped my mind but, I've wanted to contribute the same thing and it's customizable libsonnet source for a while here, so thank you for leading this!

I'll try to diff the config here against the one linked to make sure we didn't miss anything.

[clavinjune]

any other thing I should update?