[Refactor]Abstract Platform Interface for Distributed Backend and Add xccl Support for Intel XPU (#19410)

Signed-off-by: dbyoung18 <yang5.yang@intel.com>
Signed-off-by: Kunshang Ji <kunshang.ji@intel.com>
Co-authored-by: Kunshang Ji <kunshang.ji@intel.com>

vllm/platforms/rocm.py

@@ -164,6 +164,7 @@ class RocmPlatform(Platform):
     device_type: str = "cuda"
     dispatch_key: str = "CUDA"
     ray_device_key: str = "GPU"
+    dist_backend: str = "nccl"
     # rocm shares the same device control env var as CUDA
     device_control_env_var: str = "CUDA_VISIBLE_DEVICES"