Move aggregated repository statistics to critical telemetry

Created by: ebrodymoore

Aggregated repository statistics (lines of code and size of git repositories stored) should be in the critical telemetry bucket of pings as we need this for billing purposes. Slack conversation here.

@keegancsmith assigned this to you since you had the original repo stats pings, but I know you've been floating so please push this onto another team if this isn't you! 😄