scripts: utils: add include migration script

All includes are now prefixed with <zephyr/...>, even though the old
include paths can still be used when CONFIG_LEGACY_INCLUDE_PATH=y, an
option still enabled by default. Migrating large projects can be tedious
and time consuming. This patch provides a script that can be used to
migrate any Zephyr-based project to the new include path. It is used
like this:

  python $ZEPHYR_BASE/scripts/utils/migrate_includes.py \
         -p path/to/zephyr-based-project

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>