Unable to reference jwt provider when composing Gateway SecurityPolicy and HTTPRoute SecurityPolicy

*Description*:
I've configured OIDC and JWT in a SecurityConfig at the Gateway. I'd like to have a SecurityConfig per HTTPRoute to override / add `authorization`, without having to duplicate the jwt configuration.

If I don't duplicate the JWT configuration, I get the error `The SecurityPolicy "argocd-compose" is invalid: spec: Invalid value: if authorization.rules.principal.jwt is used, jwt must be defined` - the admission controller doesn't appear to be checking the merged SecurityConfig, but the SecurityConfig before it's merged.

*Repro steps*:
(lightly redacted)
```
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
name: oidc
namespace: envoy-gateway-system
spec:
targetRefs:
- group: gateway.networking.k8s.io
kind: Gateway
name: gw
oidc:
provider:
issuer: https://auth.example.com
clientID: foobar
clientSecret:
name: oidc-creds
redirectURL: https://myapp.example.com/oauth2/callback
logoutPath: /logout
cookieDomain: myapp.example.com
forwardAccessToken: true
jwt:
providers:
- name: zitadel
remoteJWKS:
uri: https://auth.example.com/oauth/v2/keys
claimToHeaders:
- claim: sub
header: X-Zitadel-Sub
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: argocd
namespace: argocd
spec:
parentRefs:
- name: gw
kind: Gateway
group: gateway.networking.k8s.io
namespace: envoy-gateway-system
hostnames:
- argocd.example.com
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: argocd-server
port: 80
---
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
name: argocd
namespace: argocd
spec:
mergeType: StrategicMerge
targetRefs:
- group: gateway.networking.k8s.io
kind: HTTPRoute
name: argocd
# Without jwt dictionary got following issue
# The SecurityPolicy "argocd-compose" is invalid: spec: Invalid value: if authorization.rules.principal.jwt is used, jwt must be defined
# If copy jwt dictionary from oidc SecurityPolicy above, works as expected
authorization:
defaultAction: Deny
rules:
- name: allow-mygroup
action: Allow
principal:
jwt:
provider: zitadel
claims:
- name: roles
valueType: StringArray
values:
- mygroup
```

*Environment*:
envoy-gateway helm 1.8.0
envoy v1.38.3

*Logs*:
N/A