Throw an ServiceNotFoundException in AbstractPluginManager when the invokable does not exist.

Mimic the same behaviour in the `AbstractPluginManager::createFromInvokable` as in the `ServiceManager::createFromInvokable`.

This could have been resolved by adding a check in the `ServiceManager::setInvokable` but that could potentially break a lot of peoples modules when they register **optional** invokables for extensions that are not loaded.