tonic options max_decoding_message_size/max_encoding_message_size

[harscoet]

Currently its not possible to define tonic options to change max_encoding_message_size and max_decoding_message_size I redefined them in KvClient and WatchClient (I didn't add max_encoding_message_size for watch client as I don't see any use case for it)

let etcd_client = etcd_client::Client::connect(["localhost:2379"], None).await.unwrap();

let etcd_kv_client = etcd_client
  .kv_client()
  .max_encoding_message_size(10* 1024 * 1024);
  .max_decoding_message_size(10* 1024 * 1024);

let etcd_watch_client = etcd_client
  .watch_client()
  .max_decoding_message_size(10* 1024 * 1024);

[davidli2010]

LGTM, thanks!