neptune: Add replica for multi region on AWS Neptune

### Describe the feature

We need a feature on CDK to add replica data on Neptune for my services that use multiple regions

### Use Case

We need to implement a multi region services in our architecture for regulations purpose on our fintech company, and we use this service to avoid fraud in our transactions.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### CDK version used

2.83.1

### Environment details (OS name and version, etc.)

python 3.7.6

Start by reviewing the existing CDK support for AWS Neptune and the AWS documentation for multi-region replicas. Clarify the expected replica model and regional configuration before identifying the relevant construct code and tests; done should mean CDK can define the requested multi-region Neptune setup with coverage for the supported configuration.

Written by the indexing model from the issue text.