(aws-lambda): Lambda shareable events

### Description

[Shareable test events](https://docs.aws.amazon.com/lambda/latest/dg/testing-functions.html#creating-shareable-events) is now available in the Lambda console. All you need to do it is setup an [Amazon EventBridge schema registry](https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-schema-registry.html) called `lambda-testevent-schemas` and then create schemas with examples with the following naming convention `_-schema`.

### Use Case

Allows you to quickly populate shareable events on your `dev`, `test` and `stage` environments

### Proposed Solution

From a UX point of view, we could simply things by just asking for the sample events you want to add ie:

```python
function.add_shareable_test_event("test_pass", test_pass_event)
function.add_shareable_test_event("test_fail", test_fail_event)
```

And to be future proof also allow for a full schema definition.

This would use a CloudFormation Custom resource under the schemas to setup these test events (as well as ensure the required registry is created). In the future, hopefully official CloudFormation support will be coming.

A prototype for this exists here: [Lambda shareable test events](https://lambda.101i.de/lambda-resources/#lambda-shareable-test-events)

### Other information

- https://docs.aws.amazon.com/lambda/latest/dg/testing-functions.html#creating-shareable-events

### Acknowledge

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

Start with the AWS Lambda shareable test events and EventBridge schema registry documentation, then review the linked prototype for the proposed API and custom-resource approach. Done should include creating the required registry and named schemas for the requested events, while supporting a full schema definition and verifying the behavior across dev, test, and stage environments.

Written by the indexing model from the issue text.