Document and review list of metrics + monitoring data in use

[seanshahkarami]

As a first step towards simplifying some different datasets we're sending, it's worth understanding the coverage we have between the different metrics and monitoring services. It may make sense to merge some of these, particularly if they already have significant overlap with each other.

This would complement issue #35 nicely for ensuring we're tracking of all of this in a tightly structured, backed up manner.