feat(s3): round-trip object attributes and tags

[cxymds]

Closes rustfs/backlog#1456

Background

The transfer-fidelity models added in #303 were still handled by conservative ObjectStore defaults, so the S3 adapter could not round-trip standard object attributes or atomically attach tags. Multipart copy also had no way to preserve the same metadata semantics as CopyObject.

Root cause

The S3 adapter only mapped Content-Type and user metadata through legacy request models. Advanced transfer methods were not overridden, and RustFS beta.10 does not safely honor full CopyObject metadata REPLACE or tagging directives.

Solution

• map all supported standard attributes and user metadata from version-aware HEAD responses
• apply attributes and deterministically URL-encoded tags atomically during PutObject
• send explicit metadata COPY for CopyObject while rejecting beta.10 metadata REPLACE and tagging gaps before any request
• preflight the effective source version for multipart metadata COPY and apply the full attribute set to CreateMultipartUpload
• preserve typed access-denied errors and cancellation boundaries
• keep checksum, storage class, SSE-C, and object-lock fields explicitly unsupported for their follow-up issues

Validation

• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• independent review completed with no remaining actionable findings