lib: sscanf: add sscanf implementation

Port sscanf implementation from mini-os and introduce new
Kconfig option to enable it: CONFIG_SSCANF. Disable by default.

Signed-off-by: Andrii Anisov <andrii_anisov@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>