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/config.go

@@ -6,7 +6,7 @@ import (
 )
 
 type evaluatorConfig struct {
-	Policies                                          []config.Policy `hash:"-"`
+	Policies                                          []*config.Policy `hash:"-"`
 	ClientCA                                          []byte
 	ClientCRL                                         []byte
 	AddDefaultClientCertificateRule                   bool
@@ -34,7 +34,7 @@ func getConfig(options ...Option) *evaluatorConfig {
 }
 
 // WithPolicies sets the policies in the config.
-func WithPolicies(policies []config.Policy) Option {
+func WithPolicies(policies []*config.Policy) Option {
 	return func(cfg *evaluatorConfig) {
 		cfg.Policies = policies
 	}