feat(core): add transfer fidelity option models

[cxymds]

Related issue

Closes rustfs/backlog#1455
Parent: rustfs/backlog#1371
Roadmap: rustfs/backlog#1361

Background and impact

The existing ObjectStore write/copy APIs can express only Content-Type and SSE-S3/SSE-KMS. Adding metadata, tags, storage class, checksums, SSE-C, retention, or legal hold directly to those public structs would break downstream struct literals, while adding SSE-C to the serializable encryption enum could expose customer key material. Backends also need an explicit way to reject advanced fields instead of silently discarding them.

Solution

• Add backend-neutral transfer fidelity models for standard object attributes, metadata/tag directives, checksum calculation or precomputed values, storage class, encryption, retention, and legal hold.
• Store SSE-C keys in zeroizing memory with redacted Debug output and exact 32-byte validation.
• Validate HTTP metadata names/values, S3 tag limits, checksum Base64/digest length, empty storage class/KMS identifiers, and copy directive consistency before mutation.
• Add additive ObjectStore transfer methods with compatibility defaults. Legacy-compatible fields delegate to existing methods; unsupported advanced behavior returns UnsupportedFeature before backend requests.
• Add a separate transfer metadata result so ObjectInfo and output schema v1 remain unchanged.
• Cover single and multipart copy compatibility, source-version consistency, trait-object dispatch, argument preservation, zero-request rejection, and encryption propagation.

Compatibility

• No protected files changed.
• No direct AWS SDK dependency was added to rc-core.
• Existing ObjectReadOptions, CopyObjectOptions, ObjectEncryptionRequest, ObjectInfo, and output schemas are unchanged.
• Existing ObjectStore implementations keep compiling because all new trait methods have defaults.

Review follow-up addressed

• Reject metadata header injection and invalid metadata header names.
• Validate checksum Base64 and algorithm-specific digest lengths.
• Enforce S3 object-tag count/key/value limits.
• Exercise inherited default methods through &dyn ObjectStore, including zero-request rejection and multipart version behavior.

Validation

• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• CARGO_BUILD_JOBS=2 cargo test --workspace
• Independent final re-review: no remaining actionable findings