(aws-iotevents): golang: export _bind so that L2 constructs can be written in Go

### Describe the feature

I want to write my own `IAction` in Go (for SNS publishing), but I cannot seem to satisfy the correct interface.

Looking at the definition:

```ts
export interface IAction {
/**
* Returns the AWS IoT Events action specification.
* @internal
*/
_bind(scope: Construct, options: ActionBindOptions): ActionConfig;
}
```

`_bind` is not exported so it is not part of the generated Go IAction.

the `aws-iot` Actions used to have `Bind` exported and I could write my own actions before CDK officially supported the DynamoDBv2 action.

Passing in a Go a struct with method:

`func (action *IoTEventSNSAction) _Bind(scope constructs.Construct, options *iotevents.ActionBindOptions) *iotevents.ActionConfig {`

results in `panic: action._bind is not a function`.

Alternatively, is there another way to achieve this?

### Use Case

I have no way to extend the functionality here, except first write a Typescript class.

### 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

2.73.0

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

macOS 13.3

Start by tracing the TypeScript IAction interface and the generated Go IAction interface to understand how the unexported _bind method is handled across languages. Check the existing aws-iot action interfaces for their exported Bind behavior, then determine whether exposing _bind preserves the intended contract and whether the generated Go interface can accept a custom SNS action.

Written by the indexing model from the issue text.