[Voxtral TTS] Support voxtral tts cfg_alpha sampling params via temperature

[y123456y78]

Purpose

• Support voxtral tts cfg_alpha sampling params via temperature
• Add corresponding unit test
• Clean up cuda graph & cuda graph test code a bit

Testing Plan

pytest -s -v \
  tests/model_executor/stage_input_processors/test_voxtral_tts_async_chunk.py \
  tests/model_executor/models/voxtral_tts/test_cuda_graph_acoustic_transformer.py \
  tests/model_executor/models/voxtral_tts/test_audio_tokenizer_parsing.py \
  tests/e2e/online_serving/test_voxtral_tts.py \
  tests/model_executor/models/voxtral_tts/test_text_preprocess.py \
  tests/e2e/offline_inference/test_voxtral_tts.py

Result