(ecr): PullThroughCacheRule L2

### Describe the feature

Implementation of AWS::ECR::PullThroughCacheRule https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ecr-pullthroughcacherule.html

### Use Case

Looks like this is missing

### 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

2.24.1

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

MacOS 12.3.1, Python 3.9

The issue links the AWS CloudFormation documentation for AWS::ECR::PullThroughCacheRule but names no repository files, entry points, or tests. Start by reading that resource specification and locating the relevant ECR constructs and tests in the CDK repository. Done means the resource is available through the CDK API with coverage for its documented properties and behavior.

Written by the indexing model from the issue text.