CLI: Limit where we warn about unset XDG_DATA_DIRS
CLI: Limit where we warn about unset XDG_DATA_DIRS

This warning is meant for interactive use, and as per #3316 it often
breaks non-interactive stuff like scripts. So, we only warn on ttys,
and only on normally interactive operations like run, install and update
to avoid warnings in cases like building (where XDG_DATA_DIRS is not
needed) or information gathering things like e.g. flatpak info.

flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak