Optimize policy iterators (#5184)

* Optimize policy iterators (go1.23)

This modifies (*Options).GetAllPolicies() to use a go 1.23 iterator
instead of copying all policies on every call, which can be extremely
expensive. All existing usages of this function were updated as
necessary.

Additionally, a new (*Options).NumPolicies() method was added which
quickly computes the number of policies that would be given by
GetAllPolicies(), since there were several usages where only the
number of policies was needed.

* Fix race condition when assigning default envoy opts to a policy

authorize/evaluator/evaluator.go

@@ -168,7 +168,7 @@ func getOrCreatePolicyEvaluators(
 			continue
 		}
 		builders = append(builders, func(ctx context.Context) (*routeEvaluator, error) {
-			evaluator, err := NewPolicyEvaluator(ctx, store, &configPolicy, cfg.AddDefaultClientCertificateRule)
+			evaluator, err := NewPolicyEvaluator(ctx, store, configPolicy, cfg.AddDefaultClientCertificateRule)
 			if err != nil {
 				return nil, fmt.Errorf("authorize: error building evaluator for route id=%s: %w", configPolicy.ID, err)
 			}