cluster_upstream_rq_total metric doesn't include directResponse HTTPRouteFilters

*Description*:

When an `HTTPRoute` has a `directResponse`, the `directResponse` status code is not included in the exported metrics.

*Repro steps*:

(This assumes a Gateway and OpenTelemetry metrics sink are configured).

```yaml
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: default-404
namespace: default
spec:
parentRefs:
- group: gateway.networking.k8s.io
kind: Gateway
name: gateway
rules:
- filters:
- extensionRef:
group: gateway.envoyproxy.io
kind: HTTPRouteFilter
name: direct-response-404
type: ExtensionRef
matches:
- path:
type: PathPrefix
value: /
name: default
---
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: HTTPRouteFilter
metadata:
name: direct-response-404
namespace: default
spec:
directResponse:
body:
inline: Not found 2
type: Inline
contentType: text/plain
statusCode: 404
```

```shell
curl http://example.com/this-is-not-found
```

This outputs `Not found 2`, but `cluster_upstream_rq_total` does not increment `envoy_response_code=404`

*Note:*
The reason for this configuration, which is no different from the default behavior, is that we like to have metrics for `404`s, as that can indicate a client/server misconfiguration. It makes sense to not include the default `404`s in metrics, it seems explicitly configuration a catch-all route should cause them to be included.