Fix ECMQmlModule for static plugins
We want the prefix to be picked up from Qt automatically. In its current state, we would need to prepend ":/" to the import paths manually.
Also, we want to initialize the generated qrc resource automatically. We can do this by setting the QT_PLUGIN_RESOURCE_INIT_FUNCTION function, which gets called before the static plugin is loaded. Because Qt creates the plugin instances before looking for the qrc files, this happens early enough.