Sockets Added Cpu Locality Connection Balancer

Added :ref:cpu_locality_balance <envoy_v3_api_field_config.listener.v3.Listener.ConnectionBalanceConfig.cpu_locality_balance> to steer each new TCP connection to the worker thread pinned to the CPU that received it, using a kernel SO_REUSEPORT BPF program. This removes the lock the exact connection balancer takes on every accept and keeps each connection on a single worker for cache and NUMA locality. It requires :ref:enable_worker_cpu_affinity <envoy_v3_api_field_config.bootstrap.v3.Bootstrap.enable_worker_cpu_affinity>, reuse port, a kernel that supports reuse port BPF steering, and a worker count no greater than the number of CPUs in the process affinity mask. When any requirement is not met the listener keeps serving with the kernel default reuse port hashing and without CPU locality. It is available on Linux only.