nk3 validate-update: Print binary checksums

[robin-nitrokey]

The nk3 validate-update command should print the checksums of the included binaries to be able to compare them to the artifacts on GitHub and/or to own firmware builds.

• lpc55: spsdk can be used to extract the MBI from the SB2 container and then parse the MBI
• nrf52: the container uses the binary while the CI produces an ihex file. either we need to produce the ihex from the binary (not trivial because intelhex adds an additional header line) or the binary from ihex (not nice because we cannot compare directly against the GitHub artifacts)
  • see also: Produce binary files instead of ihex for nrf52 nitrokey-3-firmware#511