Add metrics for created/uploaded files

[0237h]

Hey guys,

I was setting up a dashboard from the Prometheus metrics exposed by the sink and was expecting some metrics related to number of files pushed, block boundaries, etc.

The logs shows they are statistics for this:
Example

{
  "severity": "INFO",
  "timestamp": "2025-01-24T16:53:13.354844397Z",
  "logger": "substreams-sink-files",
  "message": "bundler stats",
  "file_count": 1,
  "boundary": "[103820000, 103830000)",
  "boundary_process_duration": 540.815151105,
  "upload_duration": 0,
  "data_process_duration": 523.512221366,
  "avg_upload_dur": 0,
  "total_upload_dur": 0,
  "avg_boundary_process_dur": 540.815151105,
  "total_boundary_process_dur": 540.815151105,
  "avg_data_process_dur": 523.512221366,
  "total_data_process_dur": 523.512221366,
  "logging.googleapis.com/labels": {}
}

Note

On a side note, it seems like upload_duration isn't working as expected being always set to 0

Would be awesome to get access to those through with gauge/counter/histogram Prometheus metrics.