text: Title: [Feature]: Reduce vLLM's import time
  Body: ### 🚀 The feature, motivation and pitch
  
  It takes 6s to print a version, likely because vLLM initialize the CUDA context through import
  ```
  time vllm --version
  INFO 03-17 04:53:22 [__init__.py:256] Automatically detected platform cuda.
  0.7.4.dev497+ga73e183e
  
  real    0m4.729s
  user    0m5.921s
  sys     0m6.833s
  ```
  
  This not only hurt CLI experience, but also makes users running `from vllm import LLM` experience slow startup time. 
  
  Please help us investigate this and make import time computation as lazy as possible so a simple `vllm --version` can be ran fast. 
  
  ### Alternatives
  
  _No response_
  
  ### Additional context
  
  _No response_
  
  ### Before submitting a new issue...
  
  - [x] Make sure you already searched for relevant issues, and asked the chatbot living at the bottom right corner of the [documentation page](https://docs.vllm.ai/en/latest/), which can answer lots of frequently asked questions.