feat(developer): kmc-convert: prevent processing possible circular rules of a .keylayout file 😎

[SabineSIL]

The structure of keylayout files allows multiple key-modifier combinations to be used one after the other.
We need to make sure they do not refer to themselves which might create circular rules while processing files like that.

Kmc-convert allows for 1,2 and 3 key-modifier combinations to be used one after the other. The use of more key-modifier combinations should be prevented

see PR#12564