adjust and enhance `NotRegisteredBeansReconciler`

[martinlippert]

We need to improve the NotRegisteredBeansReconciler to take advantage of the newly introduced logic to re-run reconcilers with a completely build index and to re-trigger validations across files, when necessary.

For the NotRegisteredBeansReconciler, this means:

• require complete index handling
• re-validate if bean method is added or removed (for the concrete type of the class under validation)
• re-validate if the factories file changes (adds or removes references to the class under validation)

For the reference:

3d1ccd7 introduced the feature for reconcilers to re-run with a fully build index, so that they can rely on index elements to be around for the validation checks.

ca4fc3c adds this logic to the reconcilers and indexing logic that takes care of feign client and feign config declarations.

[martinlippert]

The piece about reacting to changes of *.factories files is extracted to #1531