Make torch xla available on GPU (#29334)
* add USE_TORCH_XLA env
* rename torch_tpu to torch_xla
* better is_torch_xla_available; fix some fsdp and performance issues
* fix format
* fix bug when pjrt_device is cpu
* fix bug
* fix the deprecation handling
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Co-authored-by: anw90 <ang868@gmail.com>
Co-authored-by: wangang.wa <wangang.wa@alibaba-inc.com>
