Create config and overlay files for native_sim sample board

[kr-t]

For demo and supervisor applications, we shall have config and overlay files with precise configuration for the board - so the features in ocre-runtime and samples would work out of the box and no menuconfig would be necessary. Extra config and extra overlay files shall be part of this (offloaded sockets or TAP driver). Minimal documentation shall be written, or available documentation shall be expanded if necessary.

[casaroli]

fixed in #141