Update to the latest wit-bindgen etc. (#352)

* Update to the latest wit-bindgen etc.

Update to the latest wit-bindgen, wasm-tools, warg, and
wasi-preview1-component-adapter-provider crates.

In particular, this updates to the wasm-encoder that always uses a
leading zero byte, following WebAssembly/component-model#263.

Fixes #350.

* Update the tests for the new wit-component API.

* rustfmt

* When assigning a world a new name, update `pkg.worlds` too.