fstrim: add --listed-in <file[:file ..]>

fstrim: add --listed-in <file[:file ..]>

This new option works like --all but it allows to specify multiple
files with filesystems to make fstrim configuration more portable
between distributions. For example:

 fstrim --listed-in /etc/fstab:/proc/self/mountinfo

forces fstrim to try fstab and if unsuccessful than try mountinfo.

Addresses: https://github.com/karelzak/util-linux/issues/1019
Signed-off-by: Karel Zak <kzak@redhat.com>