[IMP] point_of_sale: Add the possibility to the IoT Box to perform a self-flashing

To be able to flash the partition on which the IoT Box is executed,
we must create a third partition and install an OS there to be able
to boot on it and flash the partition of the IoT Box

- Creation of the third partition
- Raspbian download and checksum verification
- Installation of Raspbian on the third partition
- Download the IoT image on the Raspbian partition and check the checksum
- Reboot on the Raspbian partition
- Installation of the IoT image on the second partition
- Reboot on the IoT partition
- Cleaning and deleting the third partition

closes odoo/odoo#44430

Task: 2161955
X-original-commit: 407d9a88
Signed-off-by: Quentin Lejeune (qle) <qle@odoo.com>