[wasm] Add js-api test and fix property details for some functions.

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index 24555cb26aec7510a1aad935bcf86e744a1767d3..e84078877f5edb006eded34ef88c9b829bad89f9 100644
--- a/src/wasm/wasm-module.cc
+++ b/src/wasm/wasm-module.cc
@@ -1735,7 +1735,7 @@ class WasmInstanceBuilder {
           isolate_->factory()->NewJSObject(object_function, TENURED);
       Handle<String> exports_name =
           isolate_->factory()->InternalizeUtf8String("exports");
-      JSObject::AddProperty(instance, exports_name, exports_object, READ_ONLY);
+      JSObject::AddProperty(instance, exports_name, exports_object, NONE);
     }
 
     PropertyDescriptor desc;