19346: pkg/tinydtls: allow build for AVR r=benpicco a=benpicco
19512: SUBSYSTEMS.md: add jia200x to subsystems r=benpicco a=jia200x
19513: boards/nrf52840dongle/doc: Update nrfutil pointers r=benpicco a=chrysn
### Contribution description
Nordic changed its nrfutil; this change adjust to it.
I'm not fully happy with recommending that tool at all due to its bad quality (see rambling in https://github.com/RIOT-OS/RIOT/issues/19511), but short of soldering on a debug header or touch-probing it with wires it's the only way in to the device. I may later add follow-up recommendations to switch to riotboot, but this now at least fixes the immediate issue.
### Testing procedure
* Look at the updated documentation.
### Issues/PRs references
Closes: https://github.com/RIOT-OS/RIOT/issues/19511
19514: dist/testbed-support: remove obsolete boards from iotlab archi r=benpicco a=aabadie
Co-authored-by: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Co-authored-by: Benjamin Valentin <benjamin.valentin@bht-berlin.de>
Co-authored-by: Jose Alamos <jose@alamos.cc>
Co-authored-by: chrysn <chrysn@fsfe.org>
Co-authored-by: Alexandre Abadie <alexandre.abadie@inria.fr>
429de92251