bug#44273: "total used in directory 19 available 5.2 GiB"

[積丹尼 Dan Jacobson]

Yup. fellows, that line, it turns out is for old timers, from back in the
days when people discussed "disk space".

So it should be not shown by default, and if any old-timer wants to turn
it on, they can figure out what it means on their own. (Mention that in
the docs: "dired-display-ls-nerd-line: (or
dired-display-ls-statistics-line) default nil. Contains system specific
Nurd info beyond emacs' knowledge.)

Voila, lots of programming avoided.

As far as /usr/bin/ls: that's beyond the scope of this bug.