insights: improve efficiency of snapshot/current data points over some repos

Created by: chwarwick

The initial implementation of running snapshots & recording current data points over some repos runs a global query and then filters the results down to just the requested repos. While this works, it is inefficient and has the adds the possibility that insights that would break globally will also break when run over a subset of repos.

The goal of this work is to modify the snapshot/current data point recoding worker to limit the scope of the executed queries to just the repos that the series applies to so that it can run as efficiently as possible.