Refactor Alive Monitor code to replace checkpoints with Alive Notifications

### What

The AliveMonitor code in the Launch Manager was design to support different supervision types and is therefore based on numbered checkpoints.

Now with in Score, the Launch Manager only receives alive notifications from a process - making the support of different checkpoints obsolete.

This affects multiple parts of the AliveMonitor implementation.
This ticket shall be broken down into different parts

### Acceptance Criteria (DoD)

AliveMonitor implementation is simplified to deal only with alive notification instead of numbered checkpoints

### How

_No response_