It's not possible to add them as default methods to `SpiDevice` itself,
but it's possible to do via an extension trait!
With this, you can avoid interacting with the horrible async closure hack in most
cases. You can now do `my_device.write(&buf).await`, just like with bare buses.
347: async: add SPI r=eldruin a=Dirbaio
This is an exact mirror of the blocking SPI trait (including the proposed changes in #351 ), except the following differences:
- `W: 'static` is required everywhere, otherwise complicated lifetime bounds are required in the future GATs.
Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>
