and share them using the common include file.

    rauc: Move machines specific configurations into
    dedicated include file (rauc-conf.inc) for metadata sharing.

    grub/oniro-grub-bootconf.bb: Include rauc-conf.inc. Retrieve the
    values ​​of SERIAL_CONSOLES, RAUC_SLOT_A, RAUC_SLOT_B to pass them to
    grub.cfg file.

    grub/files/grub.cfg: Use SERIAL_CONSOLES, RAUC_SLOT_A, RAUC_SLOT_B
    variables instead of hard-coding their values, to be suitable for
    different target machines.

Signed-off-by: Natalia Kovalenko <waykovalenko@gmail.com>