Switch everything to wasmtime-wasi

[jeffcharles]

Description of the change

Removing the last uses of wasi-common in favour of wasmtime-wasi.

I'm opting not to update the CHANGELOG for javy-codegen since there is nothing about this code change that should be user-facing.

Why am I making this change?

We want to standardize on wasmtime-wasi.

Checklist

• I've updated the relevant CHANGELOG files if necessary. Changes to javy-cli and javy-plugin do not require updating CHANGELOG files.
• I've updated the relevant crate versions if necessary. Versioning policy for library crates
• I've updated documentation including crate documentation if necessary.