The component manager doesn't detect cycles in the initialization of singleton components

When a singleton component triggers its own loading during its initialization (through a chain of dependencies), the component manager creates a new instance of it. In some cases this leads to a stack overflow, in other cases where the cycle breaks for some reason in the second iteration, it might also just lead to several instances of the singleton component.

The component manager should prevent that a second instance of a singleton component is created and fail with a clear error.