filc - tracking retrievals and producing CAR files

Following up on conversations happening on the data-programs/evergreen front and at the bedrock hack week, here's an issue to track the improvements we should make to filc (filclient lib).

Overarching motivation:
- automate retrieval attempt tracking so we can identify where things are failing
- provide actionable failure reports to lotus-dev and bedrock

Requirements:
- clients should be able to use filc to retrieve CIDs as CAR file
- instrument the retrieval flow from filc to produce DEBUG logs for the full lifecycle of a retrieval attempt (from initial dial to CAR output to disc or failure outcome with failure reasons)