refactor(s3-client): drop superseded per-algorithm checksum plumbing (#6700)

refactor(s3-client): remove the superseded per-algorithm checksum plumbing

Deletes the write-only RequestMetadata.add_crc pipeline (assigned but never read since the port), the dead MinIO-parity Checksum constructors and CompletePart accessor, and key_capitalized (identical to key). The five hand-rolled x-amz-checksum-* response-header if-lets in the streaming and multipart paths collapse into one checksum_header_value helper, ChecksumMode's inherent to_string becomes a Display impl, and checksum.rs drops its file-wide allow blanket now that the file is lint-clean.

Refs rustfs/backlog#1844 (PR2 of 3).

crates/s3-client/src/api_list.rs

@@ -103,7 +103,6 @@ impl TransitionClient {
                     stream_sha256: false,
                     trailer: HeaderMap::new(),
                     pre_sign_url: Default::default(),
-                    add_crc: Default::default(),
                     extra_pre_sign_header: Default::default(),
                     bucket_location: Default::default(),
                     expires: Default::default(),
@@ -206,7 +205,6 @@ impl TransitionClient {
                     stream_sha256: false,
                     trailer: HeaderMap::new(),
                     pre_sign_url: Default::default(),
-                    add_crc: Default::default(),
                     extra_pre_sign_header: Default::default(),
                     bucket_location: Default::default(),
                     expires: Default::default(),