Start migrating wasm_bindgen tests to wasm_bindgen_test (#602)

This commit starts migrating the `wasm_bindgen` tests to the `wasm_bindgen_test`
framework, starting to assemble the coffin for
`wasm-bindgen-test-project-builder`. Over time all of the tests in
`tests/all/*.rs` should be migrated to `wasm_bindgen_test`, although they may
not all want to go into a monolithic test suite so we can continue to test for
some more subtle situations with `#[wasm_bindgen]`.

In the meantime those, the `tests/all/api.rs` tests can certainly migrate!

crates/cli/src/bin/wasm-bindgen-test-runner/node.rs

@@ -76,6 +76,7 @@ pub fn execute(module: &str, tmpdir: &Path, args: &[OsString], tests: &[String])
     let path = env::var("NODE_PATH").unwrap_or_default();
     let mut path = env::split_paths(&path).collect::<Vec<_>>();
     path.push(env::current_dir().unwrap());
+    path.push(tmpdir.to_path_buf());
     exec(
         Command::new("node")
             .env("NODE_PATH", env::join_paths(&path).unwrap())