[Admin Analytics] Add usagestats pings
Created by: thenamankumar
This PR adds Admin Analytics Usage Stats Ping.
The tracking includes:
- Page views on various admin analytics pages.
- Date Range dropdown selection events to find what date range is more prefered.
- Aggregation toggle clicks between Totals & Uniques.
- Hours Saved calculator input edit counts to track if the calculator is being used.
BigQuery Schema Update: https://github.com/sourcegraph/analytics/pull/550
Test plan
- unit tests