Draft: Fix Vicinity

This merge fixes major issues in the vicinity of a node like:

• an incomplete vicinity graph
• incorrect discovery process of new vicinity nodes
• missing crucially required meta-data in the vicinity graph

This merge request is heavily inspired by the current KIRA datatracker draft by Roland Bless. The goal is that the behaviour is mostly on par with the draft with the major exception being an unsupported overflow of the StateSeqNr which will result in a panic.

Crucially the merge will also allow other use-cases to access the now more robust vicinity graph domain structure using the UseCaseContext. This might come in handy in the future for features like fast-failover. This merge also introduces new UseCaseEvents to notify other UseCases about changes in the vicinity.