Migrate Prompt to use NCrystal 4

[tkittel]

As discussed today, Prompt should be migrated to work with NCrystal 4 (probably not much to do), and work with NCrystal installed via python wheels (requires a few lines of change in CMake + to stop manually building NCrystal).

[xxcai1]

It is done in the branch dev after the commit 7015c26a.

The code is available at https://github.com/mctools/cinema-mirror.

[tkittel]

Great! Closing.