Update to the upcoming WITs

[Mossaka]

Update the WITs to follow the upcoming package format. This will not be able to land until bytecodealliance/wit-bindgen#580 and bytecodealliance/wasmtime#6390 land and possible a new version for wit-bindgen and wasmtime.

I used the package name spin:reactor for the entire WIT package. Happy to change it

[rylev]

I'm not sure what the package name should be. My first impression was fermyon/spin (much like the GitHub repo). Reactor feels much more like a world name rather than a package name.

[Mossaka]

My first impression was fermyon/spin (much like the GitHub repo). Reactor feels much more like a world name rather than a package name.

Sounds good. Changed it to fermyon:spin

[Mossaka]

I believe the upcoming June wasmtime-10 release will include the new WIT syntax changes.

[rylev]

Going to close this in favor of #1594. Thanks!