Socket options SO_SNDBUF and SO_RCVBUF support

*Description*:

Envoy will handle massive connections when used as L4 proxy. Setting the `SO_SNDBUF` and `SO_RCVBUF` socket options helps to limit the memory usage on each connection. So it would be nice to have these options in the APIs.

[optional *Relevant Links*:]

For downstream, Envoy has a `socket_options` in the listener config, https://www.envoyproxy.io/docs/envoy/v1.29.0/api-v3/config/listener/v3/listener.proto#config-listener-v3-listener

For upstream, Envoy has a `socket_options ` in the `upstream_bind_config` field of the cluster config, https://www.envoyproxy.io/docs/envoy/v1.29.0/api-v3/config/cluster/v3/cluster.proto#config-cluster-v3-cluster