Windows bigdl-nano[pytorch] issues

[cyita]

• [ ] pip install bigdl-nano[pytorch] will install 0.14.0xxxx instead of 2.1.0xxxx
• [ ] (PR #5106) unsetenv is not supported on windows, https://github.com/intel-analytics/BigDL/blob/main/python/nano/src/bigdl/nano/pytorch/init.py#L22

if 'KMP_INIT_AT_FORK' in os.environ:
    del os.environ['KMP_INIT_AT_FORK']

• [ ] intel_extension_for_pytorch is not available on windows.

torch issues on windows

• [ ] may encounter dll load issues in jupyter notebook, https://github.com/pytorch/pytorch/issues/4518