This started while adding USB MIDI support (and descriptor support is
in this change.) When seeing that I'd have to implement the MIDI class
logic twice, once for atmel-samd and once for nrf, I decided to refactor
the USB stack so its shared across ports. This has led to a number of
changes that remove items from the ports folder and move them into
supervisor.
Furthermore, we had external SPI flash support for nrf pending so I
factored out the connection between the usb stack and the flash API as
well. This PR also includes the QSPI support for nRF.
It's designed to minimize RAM footprint by using Sprites to
represent objects on the screen. The object model also facilitates
partial screen updating which reduces the bandwidth needed to display.
This is all handled in C. Python simply manipulates the objects with
the ability to synchronize to frame timing.
