Add HandlerWithAllowlist which can control exposed metrics

[CatherineF-dev]

After adding HandlerWithAllowlist, cilium or other components can exclude high cardinality metrics instead of disabling metrics collection in a running cluster.

context: https://github.com/cilium/cilium/issues/27471

I notice this pr introduces a new dependency (dto "github.com/prometheus/client_model/go"), maybe need to move HandlerWithAllowlist to another file.