Add initial support for feature tracking

[alyssabull]

It would be useful to understand what features of the datasource are being used and how they are being used. We can start by tracking some basic features to get a sense of their usage. Below are two basic things to track, we can then expand it out as we see the need for more.

• Track which mode is used, e.g. "Issues" or "StatsV2"
• Track which optional settings are used in "StatsV2": "Outcome Filter", "Reason Filter", or "Group By"