Only require str in new_with_name (#796)

* Only require `str` in `new_with_name`

It's a bit more idiomatic to have APIs require `&str` rather than
`String`, and the allocation doesn't matter much here since creating a
`Module` is pretty expensive anyway.

* Update a test

crates/api/src/instance.rs

@@ -27,7 +27,7 @@ impl Resolver for SimpleResolver<'_> {
 pub fn instantiate_in_context(
     data: &[u8],
     imports: &[Extern],
-    module_name: Option<String>,
+    module_name: Option<&str>,
     context: Context,
     exports: Rc<RefCell<HashMap<String, Option<wasmtime_runtime::Export>>>>,
 ) -> Result<(InstanceHandle, HashSet<Context>), Error> {
@@ -74,7 +74,7 @@ impl Instance {
         let (mut instance_handle, contexts) = instantiate_in_context(
             module.binary().expect("binary"),
             externs,
-            module.name().cloned(),
+            module.name(),
             context,
             exports,
         )?;

crates/api/src/module.rs

@@ -270,9 +270,9 @@ impl Module {
     /// data. The provided `name` will be used in traps/backtrace details.
     ///
     /// See [`Module::new`] for other details.
-    pub fn new_with_name(store: &Store, binary: &[u8], name: String) -> Result<Module> {
+    pub fn new_with_name(store: &Store, binary: &[u8], name: &str) -> Result<Module> {
         Self::validate(store, binary)?;
-        unsafe { Self::create(store, binary, Some(name)) }
+        unsafe { Self::create(store, binary, Some(name.to_string())) }
     }
 
     /// Creates a new WebAssembly `Module` from the given in-memory `binary`
@@ -376,8 +376,8 @@ impl Module {
 
     /// Returns identifier/name that this [`Module`] has. This name
     /// is used in traps/backtrace details.
-    pub fn name(&self) -> Option<&String> {
-        self.inner.name.as_ref()
+    pub fn name(&self) -> Option<&str> {
+        self.inner.name.as_deref()
     }
 
     /// Returns the list of imports that this [`Module`] has and must be