Update to latest WASI

[guybedford]

WASI-Virt is still on WASI 0.2.1, we should update to 0.2.2 and very soon 0.2.3.

In addition it would help to have a better error message for unsupported versions of WASI, so that it is clearer when there is a WASI versioning issue.

[ricochet]

Additionally, we should be able to support forwards and backwards level compatibility across versions, e.g. so long as the signatures match, we should be able to adapt 0.2.1 to 0.2.4's version of the interface.

[ricochet]

For anyone who bumps into this... here's a hack workaround:

wasm-tools print component.wasm -o component.wat
sed -i '' 's/@0.2.3/@0.2.1/g' component.wat
wasm-tools parse component.wat -o hack.wasm

wasi-virt --mount /virt-dir=./virt_fs -e FS=virtual --allow-all --out component_virtfs.wasm hack.wasm