Create micro:bit image with bootloader update from interface

[microbit-carlos]

Will be useful to test this feature.

[microbit-carlos]

Not yet finished: https://github.com/microbit-foundation/DAPLink/wiki/Building-micro:bit-interface-image-to-update-bootloader

[jaustin]

Jig has arrived so this can now proceed when it's prioritised.

[microbit-carlos]

Jig not required for this one as it about creating a DAPLink interface image that contains the bootloader as a blob. When this interface image is flashed, it can then update the bootloader on next reset.

[jaustin]

Bootloader update process was introduced in 0244 and current micro:bit ships with 0243/0249 combo. This task is to track investigation of how we might use the feature and whether it'll affect micro:bit users significantly if we enable it.