WebApplicationFactory alternative for Annotations framework

### Describe the feature

Microsoft provides WebApplicationFactory for AspNetCore in-memory integration testing. I think something similar could be done for AspNetCore lambdas.
It would parse generated (or created manually / via CDK) cloud formation template, and create an HttpClientHandler, which would route requests to corresponding lambda handlers instead of making actual http requests.

It should also be possible to replace configured services in DI container (in order to be possible to mock external services).

### Use Case

Integration testing for lambda serverless application project.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

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

### AWS .NET SDK and/or Package version used

Amazon.Lambda.Annotations 0.5.0-preview

### Targeted .NET Platform

.NET 6

### Operating System and version

Any