Show metric stats in admin outcomes table

[iambriccardo]

A new use case called metric_stats has been added and contains metrics about metrics. Such metrics can be queried via the metrics/query endpoint.

We would like to show a new outcomes table in the admin panel, similar to here:

The data shown there should be taken from the metrics/query endpoint and use a MRI of the metrics of metrics.

[iambriccardo]

The metric that we want to query is:

This metric refers to the total number of statsd envelope items that were captured.