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
```
executor.cleanup()
        self.assertEqual(len(executor.get_all_container_names()), 0)
        
        testutil.create_lambda_function(
            func_name=func_name, handler_file=TEST_LAMBDA_ENV, libs=TEST_LAMBDA_LIBS,
            runtime=LAMBDA_RUNTIME_PYTHON27, envvars={'Hello': 'World'})
        self.assertEqual(len(executor.get_all_container_names()), 0)
        self.assertDictEqual(executor.function_invoke_times, {})
        
        durations = []
        num_iterations = 3
        for i in range(0, num_iterations + 1):
            prev_invoke_time = None
            if i > 0:
                prev_invoke_time = executor.function_invoke_times[func_arn]
            start_time = time.time()
            self.lambda_client.invoke(FunctionName=func_name, Payload=b'{}')
            duration = time.time() - start_time
            self.assertEqual(len(executor.get_all_container_names()), 1)
            
            if i > 0:
                self.assertGreater(executor.function_invoke_times[func_arn], prev_invoke_time)
            else:
                self.assertGreater(executor.function_invoke_times[func_arn], 0)
            durations.append(duration)
        
        for i in range(1, num_iterations + 1):
            self.assertLess(durations[i], durations[0])
        status = executor.get_docker_container_status(func_arn)