Move ot WASIp3

# What
Change from WASIp2 to WASIp3 for the host<>guest interfaces.

# Why
- keeping up with the latest standards, so we don't accidently block ourselves in the future
- simplified async interfaces, see for some illustrations

# How
## Policy
I would like to avoid supporting WASIp2 & WASIp3 at the same time, so that our host code doesn't get overly complicated.

## CPython
We likely need to wait until the CPython binary is build with a version of [wasi-sdk](https://github.com/WebAssembly/wasi-sdk) and [wasi-libc](https://github.com/WebAssembly/wasi-libc) support WASIp3 first.

## Componentize-py
The WASI interface heavily leaks into the Python interface that is used by `urllib3`. We likely need to wait for a version that support WASIp3 too.

## Virtual File System
That interface likely also changes.

Start by checking whether CPython, wasi-sdk, wasi-libc, and componentize-py support WASIp3, then review how the WASI interface reaches urllib3 and the virtual file system. Done means host<>guest interfaces use WASIp3 without simultaneous WASIp2 support, including the affected virtual file system interface.

Written by the indexing model from the issue text.