…work loadbalancer

### Issue # (if applicable)

### Reason for this change

preserveClientIp was missing for GlobalAccelerator Endpoints when using a network loadbalancer.

### Description of changes

* add missing network load balancer endpoint prop.

### Description of how you validated changes

Added integration 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)

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

…work loadbalancer

preserveClientIp was missing for GlobalAccelerator Endpoints when using a network loadbalancer.

* add missing network load balancer endpoint prop.

Added integration tests.

- [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)

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