[Misc][V0 Deprecation] Add __main__ guard to all offline examples (#1837)

### What this PR does / why we need it?
Add `__main__` guard to all offline examples.

- vLLM version: v0.9.2
- vLLM main:
76b494444f

---------

Signed-off-by: shen-shanshan <467638484@qq.com>

examples/offline_inference_audio_language.py

@@ -24,9 +24,14 @@ For most models, the prompt format should follow corresponding examples
 on HuggingFace model repository.
 """
 
+import os
+
 from vllm import LLM, SamplingParams
 from vllm.assets.audio import AudioAsset
 
+os.environ["VLLM_USE_MODELSCOPE"] = "True"
+os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
+
 audio_assets = [AudioAsset("mary_had_lamb"), AudioAsset("winning_call")]
 question_per_audio_count = {
     1: "What is recited in the audio?",