metrics.Ingester: Sink by time series

[codebien]

Ingester is responsible for resolving the entire set of Sinks impacted by the ingested time series then it adds the Sample's value to the resolved set of Sinks.
Now that #2594 has been merged, the Ingester should be migrated to use the new metrics.TimeSeries struct for better efficiency, where it can use the benefits of executing a comparison between the time series structs' pointers instead to check the entire tag set.

Use case example

In a t0 where the status of the seen time series is:

http_req_duration{status:200,method:GET}
http_req_duration{method:GET}
http_req_duration{status:200}
http_req_another_one{status:200}

The Ingester in the case of a collected Sample http_req_duration{status:200,method:GET} then it resolves the dependencies with the other seen time series in a unique set where it contains the following time series http_req_duration{status:200} and http_req_duration{method:GET}. It can now resolve the relative Metric's Sinks and it invokes them passing the Sample's value.