remove global name validation

[juliusmh]

This PR introduces explicit APIs to set validation scheme for various components of prometheus.

Uses / Depends on:

• remove global name validation prometheus/common#796
• feat(prometheus): explicit label/metric name validation scheme prometheus/client_golang#1822

[aknuds1]

Instead of pkg/util/validation.IsValidLabelName and pkg/util/validation.IsValidMetricName, I think a more forward looking solution would be to implement a method pkg/util/validation.Overrides.NameValidationScheme(tenantID string) validation.NamingScheme, and use that wherever you need to validate metric or label names. It can hard-code the legacy scheme, so we don't make it configurable at first. If we have such a solution, we can easily implement the next step, which is per-tenant configurability of metric/label name validation scheme.

[aknuds1]

It doesn't seem right to me to essentially duplicate prometheus/common/model.ValidationScheme via model/validation.NamingScheme. It's going to be bad to maintain, and a potential footgun. Please see my alternative suggestion :)

[juliusmh]

Superseded by #946