Improve logging

[wilfreddenton]

{
    "severity": "INFO",
    "timestamp": "...",
    "httpRequest": {
      "requestMethod": "GET",
      "requestUrl": "/api/blocks/latest",
      "status": 200,
      "latency": "0s"
    },
    "jsonPayload": {
      "target": "indexer::api::router"
    }
  }

Do a pass over all logs and ensure we are providing jsonified objects instead of just their string representations. Ensure that the JSON log format conforms to the shape above.