444: nrf: add NVMC driver. r=lulf a=Dirbaio
I haven't implemented `embassy_traits::Flash` because I want to change it to match embedded_storage, which is much better designed.
Either way, NVMC can't do async anyway, so the best we could do is implementing the async trait in a blocking way...
Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>