RPC: Avoid calling write() so many times

Using serializePart with conn.write as the write delegate
avoid allocation but results in SO MANY write syscals that we
spend almost all of our cpu time doing syscalls.

source/agora/network/RPC.d

@@ -267,10 +267,10 @@ public class RPCClient (API) : API
                     // Send the method type
 
                     conn.wlock.lock();
-                    serializePart(method, &conn.write);
+                    conn.write(serializeFull(method));
                     // List of parameters
                     foreach (ref p; params)
-                        serializePart(p, &conn.write);
+                        conn.write(serializeFull(p));
                     conn.flush();
                     conn.wlock.unlock();
 
@@ -640,7 +640,7 @@ private void handleThrow (API) (scope API api, RPCConnection stream, Duration ti
             {
                 mixin("auto foo = ", CallMixin);
                 log.trace("[SERVER] Returning {}", foo);
-                serializePart(foo, (in ubyte[] v) { stream.write(v); });
+                stream.write(serializeFull(foo));
                 log.trace("[SERVER] Done writing...");
             }
             return;