Hello world in WASI Component Model with Wasmtime

Currently, there are three ways to have a WASI Component Model:

1. Build a preview 1 wasm module and adapt it to a component in the guest (guest-tools)
2. Build a preview 1 wasm module, load it in as a binary in the host and adapt it to a component (host-component)
3. Build a preview 2 component via cargo component (guest-cargo)

In the Rust ecosystem, the third option is preferred. But all three are provided here as a proof of concept.