Support message encryption/decryption

[bdkanand]

Currently, the NodeJs client does not support encryption/decryption which is directly impacting us in terms of consuming an encrypted message. We already have our client in place and cannot switch to Java/Python to consume encrypted methods.

The example below shows: https://github.com/streamnative/pulsar-client-node/blob/master/examples/encryption-consumer.js

// Create a consumer
  const consumer = await client.subscribe({
    topic: 'persistent://public/default/my-topic',
    subscription: 'sub1',
    subscriptionType: 'Shared',
    ackTimeoutMs: 10000,
    **privateKeyPath: "./certificate/private-key.client-rsa.pem"**
  });

The above piece of code for the example directory shows how to pass the privateKeyPath while making a call to the client.subscribe
But in actual, if you see the internal Subscribe class, it uses ConsumerConfig class which do not have any property like privateKeyPath

This feature is supported in the C++ bindings, so it seems like we only would need to expose the relevant methods as part of the underlying producer config.