vnstat: Update to 2.12

vnstat: Update to 2.12

For details see:
https://humdi.net/vnstat/CHANGES

"2.12 / 21-Jan-2024

 - Fixed
   - QueryMode documentation in configuration file didn't match implementation
     or man page description
   - Daemon didn't try to import legacy databases when --noadd was used and no
     current version database initially existed resulting in the process
     exiting even when something could have been done
   - Daemon didn't try to import legacy databases when --initdb was used and
     no current version database initially existed, this behaviour can still
     be enabled by using --noadd in combination with --initdb
   - Using --nodaemon and --initdb at the same time didn't result in an error
     being shown
 - New
   - Add 95th percentile output as --95th, also available via --alert, --json,
     --xml and image output, requires 5MinuteHours configuration to be set to
     at least 744 for storing all the necessary data
   - Add --json support for --alert
   - Database queries resulting in error exit with status 1
   - Show spinning animation at the beginning of -l / --live output line,
     visibility configurable using LiveSpinner configuration option
   - Add -ic / --invert-colors option to image output for facilitating for
     example dark mode switching without needing to have multiple separate
     color configurations
   - Add dark mode option to image output example cgi (examples/vnstat.cgi)
   - Add option 4 to QueryMode for selecting summary output of single
     interface regardless of the number of interfaces in the database
   - Add optional mode parameter to -q / --query for overriding QueryMode
     for summary output and for enabling control of summary output style
     regardless of the number of interfaces in the database
   - Add --startempty option to daemon for starting and keeping the daemon
     running even if no interfaces were discovered and the database is empty
   - Add --noremove option to daemon for disabling the automatic removal of
     interfaces from database that aren't currently visible and haven't seen
     any traffic
   - Add third mode option to --iflist and --dbiflist for getting only the
     interface count as output"

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>