Logging path hardcoded to '/dev/null', which does not exist on Windows

[grschneider]

https://github.com/PixArt-alpha/PixArt-sigma/blob/master/diffusion/utils/logger.py#L21 hardcodes the log path to "/dev/null".
On Windows11 this gives:

Traceback (most recent call last):
  File "C:\Users\Greg\Desktop\PixArt-sigma\scripts\interface.py", line 156, in <module>
    logger = get_root_logger()
  File "C:\Users\Greg\Desktop\PixArt-sigma\diffusion\utils\logger.py", line 22, in get_root_logger
    logger = get_logger(name=name, log_file=log_file, log_level=log_level)
  File "C:\Users\Greg\Desktop\PixArt-sigma\diffusion\utils\logger.py", line 68, in get_logger
    file_handler = logging.FileHandler(log_file, 'w')
  File "C:\Users\Greg\.conda\envs\pixart\lib\logging\__init__.py", line 1146, in __init__
    StreamHandler.__init__(self, self._open())
  File "C:\Users\Greg\.conda\envs\pixart\lib\logging\__init__.py", line 1175, in _open
    return open(self.baseFilename, self.mode, encoding=self.encoding,
FileNotFoundError: [Errno 2] No such file or directory: 'C:\\dev\\null'

What about using https://docs.python.org/3/library/os.html#os.devnull or passing log_file=None on Windows instead?

>>> import os
>>> os.devnull
'nul'
>>> import logging
>>> logger = logging.getLogger('test')
>>> logging.FileHandler(os.devnull, 'w')
<FileHandler \\.\nul (NOTSET)>