string CEL function isn't supported

```
spec:
...
  port: 5000
...
ingress:
...
  annotations:
    alb.ingress.kubernetes.io/healthcheck-port: "${string(spec.port)}"
```
error:
```
Message:               Resource ingress sync failed: failed to create resource: Ingress in version "v1" cannot be handled as a Ingress: json: cannot unmarshal number into Go struct field ObjectMeta.metadata.annotations of type string
```