Refactor TestVersionedValidationByFuzzing to use a declarative map,
subresourceOnly, for resources that must be validated via a specific
subresource path (like autoscaling/Scale).
GVKs not in this map default to root-level validation (""), which is
sufficient for resources that share validation logic between their root
and subresources. This replaces the previous ad-hoc special-casing
with a cleaner, extensible mapping.