Clean up logging and tags

[pricejc-sublime]

Describe the change
This PR takes a more measured and complete attempt at our trace logging:

• Override default logger and format for both frontend and backend to get JSON structured logs
• Rename timing tags so that they're more specific and add more timings; this will allow us to use them to create metrics
• Fix some tag types that were causing issues (mainly durations and times)
• Add log for Redis errors in frontend
• Add per-scanner and per-file logging