community: add Intel GPU support to ipex-llm llm integration (#22458)

**Description:** [IPEX-LLM](https://github.com/intel-analytics/ipex-llm)
is a PyTorch library for running LLM on Intel CPU and GPU (e.g., local
PC with iGPU, discrete GPU such as Arc, Flex and Max) with very low
latency. This PR adds Intel GPU support to `ipex-llm` llm integration.
**Dependencies:** `ipex-llm`
**Contribution maintainer**: @ivy-lv11 @Oscilloscope98
**tests and docs**: 
- Add: langchain/docs/docs/integrations/llms/ipex_llm_gpu.ipynb
- Update: langchain/docs/docs/integrations/llms/ipex_llm_gpu.ipynb
- Update: langchain/libs/community/tests/llms/test_ipex_llm.py

---------

Co-authored-by: ivy-lv11 <zhicunlv@gmail.com>

libs/community/tests/integration_tests/llms/test_ipex_llm.py

@@ -13,12 +13,18 @@ skip_if_no_model_ids = pytest.mark.skipif(
     not model_ids_to_test, reason="TEST_IPEXLLM_MODEL_IDS environment variable not set."
 )
 model_ids_to_test = [model_id.strip() for model_id in model_ids_to_test.split(",")]  # type: ignore
+device = os.getenv("TEST_IPEXLLM_MODEL_DEVICE") or "cpu"
 
 
 def load_model(model_id: str) -> Any:
     llm = IpexLLM.from_model_id(
         model_id=model_id,
-        model_kwargs={"temperature": 0, "max_length": 16, "trust_remote_code": True},
+        model_kwargs={
+            "temperature": 0,
+            "max_length": 16,
+            "trust_remote_code": True,
+            "device": device,
+        },
     )
     return llm