Move the apptest runner and parts of mopy to the public SDK.

mojo/tools/mopy_internal/file_hash.py

 # 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.
 
 import logging
 
 # pylint: disable=E0611
 from hashlib import sha256
 
-from mopy.memoize import memoize
+from mopy_internal.memoize import memoize
 
 _logging = logging.getLogger()
 
 @memoize
 def file_hash(filename):
   """Returns a string representing the hash of the given file."""
   _logging.debug("Hashing %s ...", filename)
   with open(filename, mode='rb') as f:
     m = sha256()
     while True:
       block = f.read(4096)
       if not block:
         break
       m.update(block)
   _logging.debug("  => %s", m.hexdigest())
   return m.hexdigest()