Resolve a content cleaner by registration key, falling back safely.
Mirrors ResolveSegmenter: an unresolvable key logs and degrades to the plain-text cleaner (whitespace normalization only) rather than throwing mid-ingestion.
Optional
Resolve a content cleaner by registration key, falling back safely.
Mirrors ResolveSegmenter: an unresolvable key logs and degrades to the plain-text cleaner (whitespace normalization only) rather than throwing mid-ingestion.