rom_get_uf2_target_partition() function

Get UF2 Target Partition This method performs the same operation to decide on a target partition for a UF2 family ID as when a UF2 is dragged onto the USB drive in BOOTSEL mode. This method potentially requires similar complexity to the boot path in terms of picking amongst versions, checking signatures etc. As a result it requires a user provided memory buffer as a work area. The work area should byte word-aligned and of sufficient size or `BOOTROM_ERROR_INSUFFICIENT_RESOURCES` will be returned. The work area size currently required is 3064, so 3K is a good choice. If the partition table has not been loaded (e.g. from a watchdog or RAM boot), then this method will return `BOOTROM_ERROR_PRECONDITION_NOT_MET`, and you should load the partition table via > first.