codepipeline_actions: No way to add CodeConnection source

### Describe the feature

I'm trying to set up CodePipeline with a GitHub source. I think this is a common flow.
I see that there is a `GitHubSourceAction` construct but it's not what I want - it wants an oauth secret. But now in the console we can go set up a "CodeConnection" to link GItHub to AWS without having to store an oauth token somewhere in secrets manager. I'd like to use that existing connection someone has created.

I found the L1 construct I want, but have no way to use it as a Source Action in CodePipeline: https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_codeconnections.CfnConnection.html

Please add support for a CodeConnections Source Action.

### Use Case

I think my use case is pretty common: using GitHub with CodePipeline.

### 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

2.150.0

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

Linux

Start with the existing GitHubSourceAction construct and the aws_codeconnections.CfnConnection L1 construct referenced in the issue, then trace how source actions are added to CodePipeline. The issue names no repository files or tests; done means GitHub can be configured as a CodeConnections source action using an existing connection without an OAuth secret.

Written by the indexing model from the issue text.