Re-add constraints to deep-copy

This re-institutes some of the rolled-back logic from previous commits. It
bounds the scope of what the deepcopy generator is willing to do with regards
to generating and calling generated functions.

hack/verify-flags/known-flags.txt

@@ -35,6 +35,7 @@ bench-workers
 bind-address
 bind-pods-burst
 bind-pods-qps
+bounding-dirs
 build-only
 build-services
 build-tag