[Admin Analytics] add admin analytics usage stats ping
Created by: thenamankumar
- Solve charts going blank for 3 months date range due to timezone issues by moving the chart's ticks generation logic to the backend from the frontend.
- Add usage stats ping for Admin Analytics page view.
- Add new events for changing calculator inputs.
- Add new events for toggling agg from totals to uniques.
- Add new events for switching date range.
- Fix font colors from black -> body.
Test plan
- unit tests written for pings
- Visit https://sourcegraph.test:3443/site-admin/analytics/code-intel in US timezone
- Select 3 months date range
- Verify chart showing correct values
- Visit https://sourcegraph.test:3443/site-admin/analytics/code-intel
- Turn on dark mode
- Verfiy the legend's colour to be white