Rework scan display

This MR improve the state of the scan display

• Cleaner split between redis and internal shell listener
• Cleaner split between application and display
• Drop DefaultScansObserver
• Speed up and reduce memory consumption (only not yet displayed data is hold)
• Handle each scan with a dedicated printer
• Data reception and display are decorrelated
  • For very fast scans we could reduce amount of print if needed

The main logic is still there. Only the architecture was reworked.