Support for testing stream-based functions

First off, I'd like to say that this project is awesome and very well documented. The provided terraform config was really helpful while I was troubleshooting.

My team owns a lambda which returns a response stream. Since the stream pattern allows for responses >6MB payload limitation, the execution of the Step Function's `executor` will fail with:

```
Invocation error (running in series): {\n \"errorMessage\": \"Response payload size exceeded maximum allowed payload size (6291556 bytes).\"
```

The implementation of the `executor` lambda uses the V2 aws-sdk, which doesn't include the `InvokeWithResponseStream` method. I've created a branch to update the `executor` lambda to be implemented with the V3 aws-sdk and could successfully get past this hurdle using this as the utils `invokeLambda` method:

```
module.exports.invokeLambda = async (lambdaARN, alias, payload) => {
const params = {
FunctionName: lambdaARN,
Qualifier: alias,
Payload: payload,
LogType: 'Tail', // will return logs
};
const lambda = utils.lambdaClientFromARN(lambdaARN);
const command = new InvokeWithResponseStreamCommand(params);
const response = await lambda.send(command);
for await (const item of response.EventStream) {
if (typeof item.PayloadChunk !== "undefined") {
console.log(Buffer.from(item.PayloadChunk.Payload.buffer).toString());
}
}
return response;
};
```
where the response has the shape of:
```
{
'$metadata': {
httpStatusCode: 200,
requestId: 'REDACTED',
extendedRequestId: undefined,
cfId: undefined,
attempts: 1,
totalRetryDelay: 0
},
ExecutedVersion: '323',
ResponseStreamContentType: 'application/vnd.amazon.eventstream',
EventStream: SmithyMessageDecoderStream {
options: {
messageStream: [MessageDecoderStream],
deserializer: [AsyncFunction (anonymous)]
}
},
StatusCode: 200
}
```

and the payload
```
:event-typePayloadChunk
:content-typeapplication/octet-stream
:message-typeevent

```

But it unfortunately appears the `LogType: 'Tail'` parameter only works with synchronously invoked functions (documented [here](https://docs.aws.amazon.com/lambda/latest/dg/API_InvokeWithResponseStream.html#API_InvokeWithResponseStream_RequestSyntax)). This means the logs containing the "Billing Duration" stats aren't returned and the `analyzer` lambda will fail because there's nothing to analyze.

I was able to work around this issue by updating my lambda to not return a payload, since I've rationalized successfully getting a real response by the power-tuner's `executor` lambda isn't all that important in measuring cost/compute. However, I thought I'd bring up this use-case and share what I was able to get working in case this comes up for anyone else.

Thanks for putting this together!