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
```
for i in range(3)
        }
        event = {
            'table_name': table_name,
            'region_name': config.DEFAULT_REGION,
            'items': [{'id': k, 'data': v} for k, v in data.items()]
        }
        self.lambda_client.invoke(
            FunctionName=function_name,
            Payload=json.dumps(event)
        )
        dynamodb = aws_stack.connect_to_resource('dynamodb')
        rs = dynamodb.Table(table_name).scan()
        items = rs['Items']
        self.assertEqual(len(items), len(data.keys()))
        for item in items:
            self.assertEqual(data[item['id']], item['data'])
        
        testutil.delete_lambda_function(function_name)
        dynamodb_client = aws_stack.connect_to_service('dynamodb')
        dynamodb_client.delete_table(TableName=table_name)
    def test_lambda_start_stepfunctions_execution(self):
        function_name = '{}-{}'.format(TEST_LAMBDA_FUNCTION_PREFIX, short_uid())
        resource_lambda_name = '{}-{}'.format(TEST_LAMBDA_FUNCTION_PREFIX, short_uid())
        state_machine_name = 'state-machine-{}'.format(short_uid())
        testutil.create_lambda_function(handler_file=TEST_LAMBDA_START_EXECUTION_FILE,
                                        func_name=function_name,
                                        runtime=LAMBDA_RUNTIME_PYTHON36)
        testutil.create_lambda_function(handler_file=TEST_LAMBDA_ECHO_FILE,
                                        func_name=resource_lambda_name,