Improve Scheduler algorithm and documentation

Currently, the Scheduler algorithm is poorly documented, hard to understand and sub-optimal in its implementation.

• Improve overal documentation;
• Improved documentation of getPriorProducersConsumers();
• Rename prior.isPrior;
• It is quadratic in scheduling time.

added Enhancement ⭐ PriorityLow labels

assigned to @olivierbichler

Started to work on documentation in !227 (merged)

mentioned in merge request !271 (merged)

Scheduler diagnosis improved in !271 (merged).

added Documentation 📖 TopicScheduler labels