private void notifyWhenStateChanged(final ConnectivityState state, final Endpoint endpoint, final ManagedChannel ch) {
        ch.notifyWhenStateChanged(state, () -> onStateChanged(endpoint, ch));
    }
GRPC RPC client implement.

@author nicholas.jxf
@author jiachun.fjc
jraft-extension/rpc-grpc-impl/src/main/java/com/alipay/sofa/jraft/rpc/impl/GrpcClient.java