[kong] update default worker count to 2

[hbagdi]

The Helm chart sets nginx_worker_processes: "1". The original motivation for this default, against the kong default of auto was users seeing resource exhaustion when they installed Kong. This usually happened with k8s worker nodes containing a larger number of CPUs/vCPUs.
With the default of 1, we run into the other problem where a lot of users run into severe performance problems, especially with KIC DB-less deployments, where a sync (POST /config) request can introduce significant latencies on proxy requests.
Given the number of external and internal reports on this specific, we should update the default value to 2.

TODO:

• Update the default value to 2 in this repository
• Update the default value to 2 in Kong Ingress Controller's repository

[mflendrich]

What is the resource consumption impact of this change?

[mflendrich]

Suggest in update instructions that users override the new default with 1 if they encounter OOM after updating.