feat(wit-bindgen-rust) Implement resource handle support for wit-bindgen-wrpc

[jacobvm04]

Closes #15. This PR implements resource support by representing resources as opaque handles. The handles are implemented as lists of bytes wrapped ResourceOwn<T> and ResourceBorrow<T> as outlined in #101.

This PR will supersede #82. This was implemented on new branch due to the significant differences between the opaque handle based approach for representing resources used here vs #82's approach that took a much more prescriptive approach to resource handling.

An example of resources being used with wRPC can be founding in the rust_bindgen test case in tests/rust.rs.

Other than revisions, I believe the main todo item left for this is to decide how to handle drops. I'm a little unsure if resource handlers should be forced to serve a drop method that clients can call, or if wRPC resource hosts and clients should implement their own drop methods that they can call on their own basis. @rvolosatovs thoughts?

[rvolosatovs]

Other than revisions, I believe the main todo item left for this is to decide how to handle drops. I'm a little unsure if resource handlers should be forced to serve a drop method that clients can call, or if wRPC resource hosts and clients should implement their own drop methods that they can call on their own basis. @rvolosatovs thoughts?

I think the resource handlers will have to implement drop, so essentially it's purely up to the "server" to manage resource lifetimes. For now, I think clients will have to manually call (fallible) drop

[rvolosatovs]

This actually looks pretty good to me!