Use `wasi-virt`-based VFS to store Python code

Currently, `componentize-py` "cheats" by assuming all required Python code will be loaded during the component pre-init step, and thus CPython won't need access to any of those files at runtime. This works surprisingly well, but will certainly break for more dynamic apps.

We should probably build a VFS by default, but also offer an option to use the "cheat" if desired.

首先追踪 componentize-py 当前如何在组件 pre-init 期间加载 Python 代码，并审查提议的基于 wasi-virt 的 VFS 方案。当默认使用 VFS 进行运行时文件访问，同时仍提供一个选项来启用现有的仅限 pre-init 的行为，并支持更动态的应用程序时，这项工作就完成了。

由索引模型根据 Issue 内容生成。