boards: rak: add support for stm32 cube programmer

Added support for stm32 cube programmer to RAK3172 module.

Tested with:
- `samples/hello_world`
- `samples/basic/blinky`

Flashed samples via stm32cubeprogrammer
- `west flash -r stm32cubeprogrammer`

Signed-off-by: Cristian Funes <cristian.funes@pragmafw.com>