These are moved:
* Display -> busdisplay.BusDisplay
* FourWire -> fourwire.FourWire
* EPaperDisplay -> epaperdisplay.EPaperDisplay
* I2CDisplay -> i2cdisplaybus.I2CDisplayBus
`paralleldisplay` is now `paralleldisplaybus` (and registered as
`paralleldisplay` too).
Bus related helpers are split out of display_core into bus_core.
It is in still displayio since it is a dependency of both
busdisplay and epaperdisplay.
Fixes#7667
Scott Shawcroft