KPI Tracking Playtest Updates

Update the KPI tracking so that it can track data per playtest rather than per device.
Feel free to ignore this, but I'm imagining:
* `Reset()` writes the data to a CSV file and then clears it
* This should create the file and headers if it doesn't exist
* Then just sloppily goes through the `MetricsData` struct and manually writes each value with CSV formatting to a file.
* `HardReset()` would do the same thing as `Reset()` currently does just so we can reset the data without writing to the CSV file
* Call `Reset()` on new game
* If you feel like it you can add it to the DevMenu reset function as well.