sensortile_box_pro board: add sample to upgrade BlueNRG SoC firmware

[avisconti]

Add sample that implement the BlueNRG SoC firmware upgrade using the AN5471 protocol on uart2 channel.

It uses blobs that must be fetched with: west blobs fetch stm32

Use of blobs approved by TSC (https://github.com/zephyrproject-rtos/zephyr/issues/74326)

(The CI for the sample is skipped because it requires the presence of a f/w blob that is not fetched by CI itself, as mentioned in https://docs.zephyrproject.org/latest/contribute/bin_blobs.html#support-and-maintenance)