CVE-2025-46342: Kyverno vulnerable to bypass of policy rules that use namespace selectors in match statements

Due to a missing error propagation in function GetNamespaceSelectorsFromNamespaceLister in pkg/utils/engine/labels.go it may happen that policy rules using namespace selector(s) in their match statements are mistakenly not applied during admission review request processing. As a consequence, security-critical mutations and validations are bypassed, potentially allowing attackers with K8s API access to perform malicious operations.