Add Series API equivalent

[davkal]

Given a set of labels, the API endpoint should return the list of available streams that match those labels.
See https://prometheus.io/docs/prometheus/latest/querying/api/#finding-series-by-label-matchers for how this is done in Prometheus.

[stale]

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[Mortega5]

any news?

[cyriltovena]

Yes 1.3 I think /cc @owen-d is focusing on this.