community[minor]: migrate bigdl-llm to ipex-llm (#19518)

- **Description**: `bigdl-llm` library has been renamed to
[`ipex-llm`](https://github.com/intel-analytics/ipex-llm). This PR
migrates the `bigdl-llm` integration to `ipex-llm` .
- **Issue**: N/A. The original PR of `bigdl-llm` is
https://github.com/langchain-ai/langchain/pull/17953
- **Dependencies**: `ipex-llm` library
- **Contribution maintainer**: @shane-huang

Updated doc:   docs/docs/integrations/llms/ipex_llm.ipynb
Updated test:
libs/community/tests/integration_tests/llms/test_ipex_llm.py

libs/community/tests/unit_tests/llms/test_imports.py

@@ -42,6 +42,7 @@ EXPECT_ALL = [
     "HuggingFacePipeline",
     "HuggingFaceTextGenInference",
     "HumanInputLLM",
+    "IpexLLM",
     "KoboldApiLLM",
     "Konko",
     "LlamaCpp",