3.13 fork: reportExtraMetrics produce unknown metrics

[bwplotka]

See: https://github.com/GoogleCloudPlatform/prometheus/pull/329/changes#r3629968314

Noticed one more thing. We have to likely expand this list with new metrics https://github.com/prometheus/prometheus/blob/47ce985126421014585c0eea59febe124eb02b81/scrape/scrape.go#L2061-L2100

While they have metadata upstream, it escapes scrapeloop cache export rely on.

Essentially reportExtraMetrics will produce unknown and unknown:gauge. This is not a default behavior, so should be ok.