Implement a feature that generates requirements.txt based on user code

[StellaHuang95]

One of our users has proposed a feature in Pylance that generates requirements.txt based on imports in project.

There are third-party tools like pipreqs that generates a requirements.txt based on your project’s imports, but user thinks it's good to have it in Pylance since they don't have to install another module, so create a discussion item here to gather other users' thoughts.