Currently minio_s3_requests_errors_total covers 4xx and
5xx S3 responses which can be confusing when s3 applications
sent a lot of HEAD requests with obvious 404 responses or
when the replication is enabled.
Add
- minio_s3_requests_4xx_errors_total
- minio_s3_requests_5xx_errors_total
to help users monitor 4xx and 5xx HTTP status codes separately.