Revision 1

- Remove the `reportError(_:)` method from `LambdaResponseStreamWriter` and instead make the `handle(...)` method of `StreamingLambdaHandler` throwing.
- Remove the `addBackgroundTask(_:)` method from `LambdaContext` due to structured concurrency concerns and introduce the `LambdaWithBackgroundProcessingHandler` protocol as a solution.
  - Introduce `LambdaHandlerAdapter`, which adapts handlers conforming to `LambdaHandler` with `LambdaWithBackgroundProcessingHandler`.
  - Update `LambdaCodableAdapter` to now be generic over any handler conforming to `LambdaWithBackgroundProcessingHandler` instead of `LambdaHandler`.

Author: aryan-25