Show instance ID on objects when debugging

Hey,

Long time I didn't open an issue here :p I miss it so here is one ^^

My use case:

> I'm using Provider and I'm proving two instance of the same BLoC. When using a breakpoint I would like to know which instance a given by provider.

Would be nice to have the instance ID of the object to be able to identify it:

Here I would like to know which CashRegisterBloc it is but can't easily.

As you can see it's done for widgets/states but not for plain objects. It's a shame as it can really simplify debugging such use case (that can happen even without provider involved).