message: network-grpc: Remove Service impl from client API
  As the client::Connection type does not implement tower::Service,
  it's pointless to offer a Service impl for client::Connect: it can't
  make Connect satisfy MakeService, and is otherwise an overcomplicated,
  unintuitive API to establish a connection. Replace with inherent method
  Connect::connect.
diff: @@ -9,7 +9,6 @@ use futures::try_ready;
  use http::uri::{self, Uri};
  use tower_grpc::BoxBody;
  use tower_h2::client::Background;
  -use tower_service::Service;
  use tower_util::{MakeConnection, MakeService};
  use std::{error::Error, fmt, mem};
  @@ -32,7 +31,7 @@ struct Origin {
  impl<P, A, C, E> Connect<P, A, C, E>
  where
  P: ProtocolConfig,
  - C: MakeConnection<A>,
  + C: MakeConnection<A> + 'static,
  E: Executor<Background<C::Connection, BoxBody>> + Clone,
  {
  pub fn new(make_conn: C, executor: E) -> Self {
  @@ -52,23 +51,8 @@ where
  self.node_id = Some(id);
  self
  }
  -}
  -
  -impl<P, A, C, E> Service<A> for Connect<P, A, C, E>
  -where
  - P: ProtocolConfig,
  - C: MakeConnection<A> + 'static,
  - E: Executor<Background<C::Connection, BoxBody>> + Clone,
  -{
  - type Response = Connection<P, C::Connection, E>;
  - type Error = ConnectError<C::Error>;
  - type Future = ConnectFuture<P, A, C, E>;
  -
  - fn poll_ready(&mut self) -> Poll<(), Self::Error> {
  - MakeService::poll_ready(&mut self.tower_connect).map_err(|e| e.into())
  - }
  - fn call(&mut self, target: A) -> Self::Future {
  + pub fn connect(&mut self, target: A) -> ConnectFuture<P, A, C, E> {
  let origin_uri = match self.origin {
  Some(ref origin) => {
  match Uri::builder()
  