redis proxy: add access log

*Title*: *Access log not available for redis proxy filter*

*Description*:
TCP proxy filter has access log which is useful for debugging. redis proxy however, does not have this field to configure. In a debugging senario, I have to changed to redis proxy to tcp proxy to verify traffic go through envoy.

[optional *Relevant Links*:]

- [Redis proxy config](https://github.com/envoyproxy/envoy/blob/master/api/envoy/config/filter/network/redis_proxy/v2/redis_proxy.proto#L18)
- Access log is only for TCP proxy and http connection manager, https://www.envoyproxy.io/docs/envoy/latest/configuration/access_log

I'm not so sure the appropriate way to debug the case above and if access log makes sense for networking filter or not. Please feel free to point something that's intended to be used instead.