`embedded-hal: 1.0` & `embedded-hal-async`

[elpiel]

I would like to discuss how we can add async impl from embedded-hal-async:0.2 and impls for embedded-hal:1.0, both currently in alpha version.

Main discussion point is how we can abstract the current trait Bus and rely on the embedded-hal traits for FourWire & ThreeWire with support for exclusive SPI bus or a shared one.

[kellerkindt]

@ryan-summers did the embedded-hal upgrade in #61 🎉