feat(elasticloadbalancingv2): enable zonal shift for network load balancer (#31990)

### Issue # (if applicable)

Closes #31983.

### Reason for this change

AWS CDK does not support for configuring zonal shift for a NLB.

### Description of changes

Add `zonalShift` prop to `NetworkLoadBalancerProps`

### Description of how you validated changes

Add both unit and integ tests.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: badmintoncryer

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2/test/integ.nlb.attributes.js.snapshot/aws-cdk-nlb-attributes-integ.assets.json

@@ -406,6 +406,10 @@
      {
       "Key": "dns_record.client_routing_policy",
       "Value": "partial_availability_zone_affinity"
+     },
+     {
+      "Key": "zonal_shift.config.enabled",
+      "Value": "true"
      }
     ],
     "Scheme": "internal",