boards: rak: add support RAK3172 breakout board

Added rak3172 breakout board which is base on stm32wle5cc chip.

Testd with:
    - `samples/hello_world`
    - `samples/subsys/shell/shell_module`

Flashed samples via pyOCD:
    - west flash

Signed-off-by: Kenneth Lu <kuohsianglu@gmail.com>