Various improvements of the Scarb package

[TAdev0]

@b-j-roberts I improved the cairo codebase overall :

• added the edition 2023_11 (which is now the default when creating a scarb package), which actives visibility feature and highlighted many visibility issues. Its nice to do it now as in a few release it will be mandatory to make every item that require it pub
• improved in the way values are returned in the codebase, as a single expression without the return keyword
• replaced the QuestClaimed event and the IPixelQuest interface at the right place for clarity

[b-j-roberts]

Could you update the Dockerfiles to reflect this change, like here

art-peace/backend/Dockerfile

Line 12 in bf05739

RUN /bin/bash /root/.local/bin/snfoundryup --version 0.20.0

Either manually change them to 0.21.0 or set up a way for the Dockerfile to properly import the changed value if you'd find that interesting.

[TAdev0]

@b-j-roberts will change manually for now if this is ok for you