Server Worker Cpu Affinity

Added :ref:enable_worker_cpu_affinity <envoy_v3_api_field_config.bootstrap.v3.Bootstrap.enable_worker_cpu_affinity> to pin each worker thread to a distinct CPU from the process affinity mask, worker i to the i-th CPU in ascending order. This improves CPU cache and NUMA locality for high concurrency deployments on bare metal. It is available on Linux only and is ignored on other platforms.