Warnings in `witx-bindgen-gen-wasmtime`'s generated code

[fitzgen]

Would be nice not to have them, or at least suppress them. I'm dealing with other things at the moment, but figured I should post this for posterity.

warning: unused import: `core::convert::TryFrom`
    --> /home/nick/witx-bindgen/target/debug/build/witx-bindgen-gen-wasmtime-ba45af0c7ded77e4/out/import/wasi_next/bindings.rs:3438:9
     |
3438 |     use core::convert::TryFrom;
     |         ^^^^^^^^^^^^^^^^^^^^^^
     |
     = note: `#[warn(unused_imports)]` on by default

warning: unused import: `witx_bindgen_wasmtime::rt::bad_int`
    --> /home/nick/witx-bindgen/target/debug/build/witx-bindgen-gen-wasmtime-ba45af0c7ded77e4/out/import/wasi_next/bindings.rs:3439:9
     |
3439 |     use witx_bindgen_wasmtime::rt::bad_int;
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: unused import: `core::convert::TryFrom`
    --> /home/nick/witx-bindgen/target/debug/build/witx-bindgen-gen-wasmtime-ba45af0c7ded77e4/out/import-tracing-and-custom-error/wasi_next/bindings.rs:4253:9
     |
4253 |     use core::convert::TryFrom;
     |         ^^^^^^^^^^^^^^^^^^^^^^

warning: unused import: `witx_bindgen_wasmtime::rt::bad_int`
    --> /home/nick/witx-bindgen/target/debug/build/witx-bindgen-gen-wasmtime-ba45af0c7ded77e4/out/import-tracing-and-custom-error/wasi_next/bindings.rs:4254:9
     |
4254 |     use witx_bindgen_wasmtime::rt::bad_int;
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: unused import: `core::convert::TryFrom`
    --> /home/nick/witx-bindgen/target/debug/build/witx-bindgen-gen-wasmtime-ba45af0c7ded77e4/out/import-async/wasi_next/bindings.rs:3576:9
     |
3576 |     use core::convert::TryFrom;
     |         ^^^^^^^^^^^^^^^^^^^^^^

warning: unused import: `witx_bindgen_wasmtime::rt::bad_int`
    --> /home/nick/witx-bindgen/target/debug/build/witx-bindgen-gen-wasmtime-ba45af0c7ded77e4/out/import-async/wasi_next/bindings.rs:3577:9
     |
3577 |     use witx_bindgen_wasmtime::rt::bad_int;
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^