InstanceProps: Unable to set CACertificateIdentifier

### Describe the feature

Following this issue: https://github.com/aws-cloudformation/cloudformation-coverage-roadmap/issues/211 ability to set the CACertificateIdentifier was supported in Cloudformation, which i see is also supported in the DBInstance type in CDK. The issue is that if someone wants to use InstanceProps, they have no way via CDK to fix the issue.

### Use Case

When regularly needing to update cert auth identifiers via CDK with InstanceProps, there is no way to do so.

### Proposed Solution

allow passing the CACertificateIdentifier property to avoid drift in infra code vs actual infra

### Other Information

_No response_

### Acknowledgements

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

### CDK version used

2.118.0 (build a40f2ec)

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

MacOS, Sonoma 14.6...

Start by comparing the DBInstance type, which already supports CACertificateIdentifier, with the InstanceProps path described in the issue. Trace how InstanceProps is converted into the DBInstance configuration and inspect the related tests. Done means users can provide CACertificateIdentifier through InstanceProps and the behavior is covered by tests.

Written by the indexing model from the issue text.