scripts: compliance: add a compliance check to keep blocks of code sorted

This allows defining a list within two marker (zephyr-keep-sorted-start
and zephyr-keep-sorted-stop), and have the CI validate that the block is
kept sorted every time stuff gets added to it.

This is mainly for Kconfig and CMake include lists so that there's no
ambiguity on where to add new stuff.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>