events: log group target

### Describe the feature

In #10598, the author added support for CloudWatch Logs log group as a target of an EventBridge event bus. The author noted that at that time, CloudFormation did not have support for CWL resource policy, they used a custom lambda to manipulate the policy. Since then, CFN added the resource support and another author added support in #17015.

Now the custom resource added in #10598 can be removed in favour of the native support.

Note that this may be a breaking change as CDK needs to manage the resource policy by importing it to the stack.

### Use Case

Removing tech debt. Custom resource lambda functions require S3 bucket to provision the code.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

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

### CDK version used

2.29.0

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

N/A

Review the existing log-group target implementation from #10598 and the native CloudFormation resource-policy support added in #17015. Confirm the custom-resource Lambda path can be removed without losing policy management, and verify that the EventBridge target still provisions correctly; the issue names no files or tests to run.

Written by the indexing model from the issue text.