Add edge byte and cacheable byte metrics
Six new stats related to edge byte and cacheable byte ratios have been added: edge_hit_resp_body_bytes, edge_hit_resp_header_bytes, edge_miss_resp_body_bytes, edge_miss_resp_header_bytes, origin_cache_fetch_resp_body_bytes, and origin_cache_fetch_resp_header_bytes.
Prior change: CLI v1.4.0
Following change: Fastly Terraform Provider 0.40.0
