fix: move wit_* packages into wit-bindgen dir

[asteurer]

For clarity, I prefer to house the wit_* files in a shared directory.

@ricochet You had mentioned that you might like to move the wit directory in go-modules to componentize-go and store the wit_* files there. I'm worried about confusion arising from mixing new code with legacy code. I figured that it would be clearer to people that the wit_* files are associated with wit-bindgen if we organize them as such. I'm definitely open to discussion, so let me know what you think 😃.

Note: I relied on an LLM's suggestions for how to handle moving the wit_* files into the wit-bindgen directory. It's entirely possible that the docs/wit-bindgen setup isn't going to work haha

[ricochet]

Oh you know I hadn't actually considered moving wit. I was more concerned about any go referenced from the root for go-modules. My main advice is that since you aren't the legacy tool, you should pick the preferred package names.

One option to consider, place public api's in pkg, e.g. go.bytecodealliance.org/pkg. Most go projects aim for shorter names where they can. Looking at the current structure, the most idiomatic package names in my opinion would be:

• go.bytecodealliance.org/pkg/wit/types
• go.bytecodealliance.org/pkg/wit/async
• go.bytecodealliance.org/pkg/wit/runtime

vs go.bytecodealliance.org/wit-bindgen/wit_types with inconsistent hyphen/underscores.