(aws-cdk-lib): CloudFormation support for SNS platform application

### Describe the feature

Last time I checked CDK did not support `CfnPlatformApplication` and using something like a custom resource was suggested as an alternative. Is it possible to introduce a new construct so I can remove the custom resource? It should have API parity with [CreatePlatformApplication](https://docs.aws.amazon.com/sns/latest/api/API_CreatePlatformApplication.html).

### Use Case

More infrastructure code can be defined in CDK removing the need for a custom resource and introducing failure points with custom resource lifecycle management.

### 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

### AWS CDK Library version (aws-cdk-lib)

2.234.1

### AWS CDK CLI version

2.1100.1

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

NA

Start by inspecting the aws-cdk-lib SNS constructs and the CloudFormation CfnPlatformApplication resource, then compare the requested surface with the AWS CreatePlatformApplication API documentation. Done means a supported CDK construct provides API parity, replaces the custom-resource use case, and includes the repository's corresponding tests.

Written by the indexing model from the issue text.