cdx loader: ensure that if duplicate cdx is found for the same timestamp, the entry with status code <300 is preferred
extend the optimization that processes revisit records first: second process all non-revisit with status >= 300, then resources with status <300 to ensure that if duplicates occur, the last resource will override previous entries for same url + timestamp (related to webrecorder/browsertrix-crawler#635)
cdx loader: ensure that if duplicate cdx is found for the same timestamp, the entry with status code <300 is preferred