As an enhancement to https://github.com/localstack/localstack/pull/1194

It would be really helpful to send the Lambda name, either as data, a header, or as part of the URL.

At code location: https://github.com/localstack/localstack/blob/03c6f4bf250edd18eb818ed65090f508636b0bff/localstack/services/awslambda/lambda_api.py#L696

I can likely open a PR to handle this given some feedback on the feature and potential design.

Right now all I see is the following (using `npx http-echo-server`):
```
[socket#8] event: data
--> POST / HTTP/1.1
--> Host: 192.168.1.x:3000
--> User-Agent: python-requests/2.22.0
--> Accept-Encoding: gzip, deflate
--> Accept: */*
--> Connection: keep-alive
--> Content-Length: 9
--> Content-Type: application/x-www-form-urlencoded
-->
-->
[socket#8] event: data
--> Name=test
```
runtime=LAMBDA_RUNTIME_PYTHON36)
        queue_url = sqs_client.create_queue(QueueName=queue_name)['QueueUrl']
        event = {
            'message': 'message-from-test-lambda-{}'.format(short_uid()),
            'queue_name': queue_name,
            'region_name': config.DEFAULT_REGION
        }
        self.lambda_client.invoke(
            FunctionName=function_name,
            Payload=json.dumps(event)
        )
        
        def receive_message():
            rs = sqs_client.receive_message(QueueUrl=queue_url, MessageAttributeNames=['All'])
            self.assertGreater(len(rs['Messages']), 0)
            return rs['Messages'][0]
        message = retry(receive_message, retries=3, sleep=2)
        self.assertEqual(message['Body'], event['message'])
        
        testutil.delete_lambda_function(function_name)
        sqs_client.delete_queue(QueueUrl=queue_url)
    def test_lambda_put_item_to_dynamodb(self):
        table_name = 'ddb-table-{}'.format(short_uid())
        function_name = '{}-{}'.format(TEST_LAMBDA_FUNCTION_PREFIX, short_uid())
        aws_stack.create_dynamodb_table(table_name, partition_key='id')
        testutil.create_lambda_function(handler_file=TEST_LAMBDA_PUT_ITEM_FILE,
                                        func_name=function_name,
                                        runtime=LAMBDA_RUNTIME_PYTHON36)
        data = {
            short_uid(): 'data-{}'.format(i)