Review error messages

[devmatteini]

1. Add source to MongoError (NOTE: the types are just WIP)

export class MongoError extends Data.TaggedError("MongoError")<{
  source: {
    _tag: "Db"
    dbName: string
  } | {
    _tag: "DocumentCollection" | "Collection" | "FindCursor"
    dbName: string
    collectionName: string
  }
  message: string
  innerError: MongoError_
}> {
}

2. MongoError.message should interpolate inner error message ${message}: ${innerError.message}
3. Pass source to mongoErrorDie and mongoErrorStream
4. Each user of MongoError will implement a specialized function to set the right source