Allow to control if the bulk request (or the shard level bulk requests that spawn from a single bulk request) are compressed or not. Currently, it is compressed, but with the changes done on better slicing and dicing the network buffer, it actually might behave better when its not compressed (at the expense of more data transfered over the wire). We will keep the default true as the existing behavior, and open a different issue if it makes sense to change the default to false.