Mojo: Move mojo/public/bindings/tests/*.mojom to mojo/public/interfaces/bindings/tests/.

mojo/public/interfaces/bindings/tests/sample_interfaces.mojom

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module sample {
 
 [Peer=ProviderClient]
 interface Provider {
   EchoString(string a) => (string a);
   EchoStrings(string a, string b) => (string a, string b);
   EchoMessagePipeHandle(handle<message_pipe> a) => (handle<message_pipe> a);
 };
 
 [Peer=Provider]
 interface ProviderClient {
 };
 
 }