Enable propogation of fatal errors through io.Reader responses

[bmoffatt]

Is your feature request related to a problem? Please describe.

A handler can gracefully force the process to be restarted by returning a messages.InvokeResponse_Error with ShouldExit = true. The usual way this happens is when the function panics, but pass-through is allowed too on the handler's error value

aws-lambda-go/lambda/errors.go

Lines 20 to 22 in caace58

	if ive, ok := invokeError.(messages.InvokeResponse_Error); ok {
	return &ive
	}

However, there's not an equivalent when the response value is a reader.

Describe the solution you'd like

Goal should be able to make this:

type fatalReader struct{}
func (r *fatalReader) Read(_ []byte) (int, error) {
  return 0, messages.InvokeResponse_Error{Type: "IDK", Message: "fatal", ShouldExit: true}
}
func handler() (any, error) {
  return fatalReader{}, nil
}

result in the same logging and error reporting as this:

func hander() (any, error) {
  return nil, messages.InvokeResponse_Error{Type: "IDK", Message: "fatal", ShouldExit: true}
}

Describe alternatives you've considered

Might also expose something like

aws-lambda-go/lambda/errors.go

Lines 35 to 46 in caace58

	func lambdaPanicResponse(err interface{}) *messages.InvokeResponse_Error {
	if ive, ok := err.(messages.InvokeResponse_Error); ok {
	return &ive
	}
	panicInfo := getPanicInfo(err)
	return &messages.InvokeResponse_Error{
	Message: panicInfo.Message,
	Type: getErrorType(err),
	StackTrace: panicInfo.StackTrace,
	ShouldExit: true,
	}
	}

in the public API, to make the construction of these fatal errors easier.