xpu: enable xccl distributed backend (#3401)
xccl distributed backend is available for XPU device backend starting
from torch 2.7 (requires torch built with `USE_XCCL=1 USE_C10D_XCCL=1`).
This change is verified with the following Transformers tests:
* `tests/extended/test_trainer_ext.py`
* `tests/trainer/test_trainer_distributed.py`
This commit does not impact IPEX which currently remains using custom
distributed backend.
Signed-off-by: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
