Use flash id on RP2040 and chip id on RP2350

[Poofjunior]

Following Related: #59, we'll need to make sure the ID read over Harp protocol is consistent with the Harp protocol. Currently, the byte order may or may not be consistent when using pico_get_unique_board_id (See: raspberrypi/pico-sdk#2291).

We'll need to be using flash_get_unique_id for the RP2040, and we'll

The main change needs to happen here: https://github.com/harp-tech/core.pico/blob/main/firmware/src/harp_core.cpp#L39