bug#73166: shell-autorized-directories

[Nicolas Graves]

According to current uses of the XDG base dirs specification, I think
guix shell-autorized-directories is in the wrong place, and should
instead be in $XDG_STATE_HOME/guix/

direnv uses $XDG_STATE_HOME too to store authorized directories, and it
also makes more sense in the context of immutable configs

WDYT? Should we implement this change? The tricky thing might be the
migration for those files. Maybe we should also add a --allow argument
to guix shell to make it easier to add files.

-- 
Best regards,
Nicolas Graves