Fixing following problems:
Issue number one:
Enable mod with a23 compatibility in a23b.
Save configuration.
Start a24.
Better result:
Mod will be enabled and invisible in mod selection screen producing various errors.
Worse result:
Game will crash and refuse to start.
Show splachscreen with information about invalid mods in config on startup.
Issue number two:
Mods can silently set loaded mods without restarting the engine, so mods can unlist themselves from compatibility detection.
Another fixes:
Display in enabled mods really enabled mods as current logic confuses players about which mods they have enabled and is not helpful (ref #4881)
Note:
this will not solve issue with mods claiming being compatible with engine version while in fact being incompatible.