Simplify reflection of classes generated by annotations framework

### Describe the feature

I'm using reflection to find the class generated by the annotation framework.

Whilst the approach is easily reproducible because the class name is "{Class}_{Method}_Generated" and the method is Method, it would be easier if the generated class was decorated with a attribute (possibly one coming from the BCL) that can be used to quickly find the generated class given the original class/function.

Additionally, it would be great if the generated class had the method with a fixed name like Handle or whatever.

Using a marking attribute and maybe even some interface with a single Handle method would make the process easier and less relying on internal implementation.

### Use Case

I'm working on a tool to improve development experience when working with Annotations Lambda

### 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

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

Any

### Targeted .NET Platform

.NET 8 + Aspire

### Operating System and version

Any

Non vengono indicati file o test. Inizia tracciando il modo in cui l’annotation framework genera classi denominate "{Class}_{Method}_Generated" e il modo in cui i consumer le individuano attualmente tramite reflection. Il lavoro sarà completato quando saranno stati concordati un attributo di metadati e un contratto stabile di metodo o interfaccia per individuare e invocare la classe generata.

Scritto dal modello di indicizzazione a partire dal testo della issue.