Implement Asynchronous Processing Using C Async Function

[k2la]

Currently, asynchronous processing in this client library is implemented by using NAPI::AsyncWorker.
e.g. https://github.com/apache/pulsar-client-node/blob/master/src/Producer.cc#L89-L120

We used AsyncWorker because segmentation fault about NAPI objects occurred in callback registered with C async function.
FYI: nodejs/node-addon-api#457

The throughput of asynchronous processing using NAPI::AsyncWorker is lower than that using C async function(e.g. pulsar_client_create_producer_async).

Therefore, we want to use C async function in order to make performance better.

[pradeep-mishra]

any update on this?

[nkurihar]

@pradeep-mishra
Sorry, there is no update.
As described in #56, ThreadSafeFunction may solve this issue but we haven't tried yet.

[nkurihar]

Now AsyncWorker is replaced with async functions: #200