Errors API query optimizations

We swept through the errors API endpoints and replaced each query with a tuned version.

1. The top-errors, error-detail, errors timeseries, errors breakdown, and errors overall endpoints have all been optimized.
2. Improved accuracy of total-view and percentage calculations in errors responses.
3. The errors breakdown now correctly handles null grouping keys instead of dropping rows.
4. Removed unnecessary fields from error responses to reduce payload size.