Expose throttleTimeout on the command line

[rg0now]

The constant throttleTimeout controls the time under which config generation is suppressed. The idea is that we do not want to re-generate the config and update the API server every time one of our watchers update a resource in the local storage since the config rendering pipeline is expensive. Rather, every time a watcher triggers an update we start a timer to wait throttleTimeout msecs and we completely suppress all config rendering triggers until the timer ticks. This decreases the CPU footprint of the operator at the cost of artificially delaying all updates with at most throttleTimeout msecs.

In large clusters with massive control plane churn, the hardcoded 250 msec timeout would be too little. This enhancement request covers:

• make throttling the default: remove DefaultEnableRenderThrottling and EnableRenderThrottling and change the code equally to as if EnableRenderThrottling=true was in effect,
• expose throttleTimeout to the command line and as an ENV variable.