Fission: Environment Runtime.Container and Builder.Container SecurityContext bypass allows privileged pod creation

Summary A follow-up bypass of the round-4 PodSpec hardening GHSA-gx55-f84r-v3r7, GHSA-wmgg-3p4h-48x7, GHSA-v455-mv2v-5g92. Those advisories validate and sanitize the PodSpec spec.runtime.podSpec / spec.builder.podSpec / function.spec.podSpec, but the Environment CRD also exposes...