Add an initial wasi-nn implementation for Wasmtime (#2208)

* Add an initial wasi-nn implementation for Wasmtime

This change adds a crate, `wasmtime-wasi-nn`, that uses `wiggle` to expose the current state of the wasi-nn API and `openvino` to implement the exposed functions. It includes an end-to-end test demonstrating how to do classification using wasi-nn:
 - `crates/wasi-nn/tests/classification-example` contains Rust code that is compiled to the `wasm32-wasi` target and run with a Wasmtime embedding that exposes the wasi-nn calls
 - the example uses Rust bindings for wasi-nn contained in `crates/wasi-nn/tests/wasi-nn-rust-bindings`; this crate contains code generated by `witx-bindgen` and eventually should be its own standalone crate

* Test wasi-nn as a CI step

This change adds:
 - a GitHub action for installing OpenVINO
 - a script, `ci/run-wasi-nn-example.sh`, to run the classification example

scripts/publish.rs

@@ -64,6 +64,7 @@ const CRATES_TO_PUBLISH: &[&str] = &[
     "wasmtime",
     "wasmtime-wiggle",
     "wasmtime-wasi",
+    "wasmtime-wasi-nn",
     "wasmtime-rust-macro",
     "wasmtime-rust",
     "wasmtime-wast",
@@ -308,7 +309,10 @@ fn verify(crates: &[Crate]) {
             .arg("--manifest-path")
             .arg(&krate.manifest)
             .env("CARGO_TARGET_DIR", "./target");
-        if krate.name.contains("lightbeam") || krate.name == "witx" {
+        if krate.name.contains("lightbeam")
+            || krate.name == "witx"
+            || krate.name.contains("wasi-nn")
+        {
             cmd.arg("--no-verify");
         }
         let status = cmd.status().unwrap();