Implement RDF Dataset Canonicalization (RDFC-1.0) with Canonical N-Quads Output

### Version

jena-5.5.0

### Feature

### Description:
Implement W3C RDF Dataset Canonicalization (RDFC-1.0) algorithm in Apache Jena with output in canonical N-Quads format. This enables deterministic serialization of RDF datasets by assigning canonical identifiers to blank nodes.

References:
- RDFC-1.0 Algorithm: https://www.w3.org/TR/rdf-canon/
- Canonical N-Quads Format: https://www.w3.org/TR/rdf12-n-quads/#canonical-quads
- W3C Test Suite: https://github.com/w3c/rdf-tests/tree/main/rdf/rdf12/rdf-n-quads/c14n and https://w3c.github.io/rdf-canon/tests/

### Tasks:

- [ ] Create NQuadsCanonicalWriter class extending WriterDatasetRIOTBase
- [ ] Add NQUADS_CANONICAL format constant to RDFFormat
- [ ] Register canonical writer factory in RDFWriterRegistry
- [ ] Implement RDFC10Canonicalizer with complete RDFC-1.0 algorithm
- [ ] Create HashUtils for SHA-256 hash computations and lexicographic sorting
- [ ] Implement CanonicalIssuer for _c14n_N blank node identifier assignment
- [ ] Add DatasetProcessor for blank node extraction and dataset processing
- [ ] Download and integrate W3C canonicalization test suite to jena-arq/testing/rdf12-wg/rdf-n-quads-c14n/
- [ ] Update Scripts_RIOT_c14n.java test factory following existing RIOT patterns
- [ ] Implement RDFCanonicalizationTest for algorithm validation leveraging https://w3c.github.io/rdf-canon/tests/
- [ ] Add writeCanonical() and canonicalizeDataset() methods to RDFDataMgr
- [ ] Add --canonical flag support to riot command line tool
- [ ] Update documentation and create usage examples

### Are you interested in contributing a solution yourself?

Yes

Start with the existing RIOT writer patterns, RDFFormat, RDFWriterRegistry, RDFDataMgr, and Scripts_RIOT_c14n.java, then read the RDFC-1.0 specification and referenced W3C tests. The work is complete when canonicalization, canonical N-Quads output, registry and CLI support, documentation, and the listed W3C validation tests are integrated.

Written by the indexing model from the issue text.