verification/dot2c: Remove __buff_to_string() and cleanup
str.join() can do what __buff_to_string() does. Therefore replace
__buff_to_string() to make the scripts more pythonic.
Also clean and remove some intermediate functions.
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20251126104241.291258-7-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>