Support (and provide tests and examples for) multithreading

Now that WASI-SDK 34 has been released with `wasm32-wasip3` support for pthreads via the Component Model's cooperative multithreading feature, we should be able to support multithreading in Python code. Alex Crichton has [run the CPython test suite with multithreading enabled](https://github.com/WebAssembly/wasi-libc/pull/850) with a few patches. In theory, things should "just work" once we apply those patches to the CPython fork we're using in this project.

Note that #242 is a prerequisite for this.

Inizia esaminando la issue preliminare #242, il fork di CPython utilizzato da questo progetto e le patch discusse in wasi-libc PR #850. Abilita il supporto pthreads di WASI-SDK 34, quindi verifica la suite di test di CPython e aggiungi gli esempi e i test di multithreading richiesti.

Scritto dal modello di indicizzazione a partire dal testo della issue.