GCS pubsub has been the default for awhile. There is little chance that we would need to revert back to Redis pubsub in future. This is the step in removing Redis pubsub, by first removing the `enable_gcs_pubsub()` feature guard.
As we are turning redisless ray by default, dashboard doesn't need to talk with redis anymore. Instead it should talk with gcs and gcs can talk with redis.
This PR contains most of the fixes @iycheng made in #21232, to make tests pass with GCS bootstrapping by supporting both Redis and GCS address as the bootstrap address. The main change is to use address_info["address"] to obtain the bootstrap address to pass to ray.init(), instead of using address_info["redis_address"]. In a subsequent PR, address_info["address"] will return the Redis or GCS address depending on whether using GCS to bootstrap.
