aws_cloudfront_origins: OriginGroup support custom originId

### Describe the feature

OriginGroup does not appear to support setting an explicit originId currently. The auto-generated ID is very long and hard to read. We would like to set the originId as with other origin types such as HttpOrigin or RestApiOrigin.

### Use Case

Create easy to read origin IDs for Origin Groups so we can more easily understand the configuration when looking at it in the CloudFront console.

### Proposed Solution

Add originId to OriginGroupProps.

I might be able to implement this; I'm not very familiar with CDK internals but it seems that wherever the auto-generated ID is created, it could instead use the explicit prop if set. I could use a little hint on where this happens.

### Other Information

_No response_

### Acknowledgements

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

### CDK version used

2.158.0

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

macOS

Start by locating OriginGroupProps and the code that creates the auto-generated OriginGroup ID. Trace how other origin types accept and use an explicit originId, then identify the relevant tests for OriginGroup behavior. Done means OriginGroup supports a readable explicit originId while retaining the generated ID when no prop is supplied.

Written by the indexing model from the issue text.