feature(wren-ai-service): refactor the query understanding pipe with async

[paopa]

This is a draft PR to allow members to test and compare the performance of synchronous and asynchronous LLM components.

• The Locust file is located in the tools folder. You can execute the following command to start Locust:

  poetry run locust -f ./tools/locust_pipe.py
  

• To try the synchronous LLM, check out the commit aca00d6.

• The asynchronous LLM is in the current head commit.