Revert "[Dist] New distributed data preparation pipeline (#4386)" (#4391)

This reverts commit 71ce1749.

tools/utils/files.py

-import os
-from contextlib import contextmanager
-import logging
-from numpy.lib.format import open_memmap
-
-@contextmanager
-def setdir(path):
-    try:
-        os.makedirs(path, exist_ok=True)
-        cwd = os.getcwd()
-        logging.info('Changing directory to %s' % path)
-        logging.info('Previously: %s' % cwd)
-        os.chdir(path)
-        yield
-    finally:
-        logging.info('Restoring directory to %s' % cwd)
-        os.chdir(cwd)