spin-deps is broken for rust

[fibonacci1729]

When using spin-deps inside of a rust project, the current code that is generated does not build. The macro that is generated uses the re-exported wit-bindgen macro from the spin-rust-sdk which runs into errors when trying to point to the input wit files at .wit/components/*. Secondly, the wit files written into that directory uses a multi-package package wit file which is not currently supported by the version of wit-parser (0.13.0) that is used by the re-exported spin-rust-sdk wit-bindgen (0.16.0).

I'm not entirely sure how to address this but i see 2 options depending on the priority:

1. Upgrade the version of wit-bindgen that spin-rust-sdk is using. There have been previous attempts to do this however it was decided to revert the upgrade because of FUD.
2. Switch back to how spin-deps was generating rust code prior to the recent refactors over the last year.

[itowlson]

Oh man, we only just did a major version bump on the Rust SDK - we should have revved wit-bindgen at the same time...