This drops the now unused `ATMEGA32U4_KEYBOARD`, `ATMEGA32U4_DEVICE_PROPS`,
`ATMEGA_KEYSCANNER_PROPS`, `ATMEGA32U4_DEVICE`, `ATMEGA_KEYSCANNER_PROPS`, and
`ATMEGA_KEYSCANNER_BOILERPLATE` macros.
These were macros that made the code less verbose, but none of them were
future-proof, and all of them were pretty opaque. Using them did not help one to
understand the code.
All use of these have been changed to use the raw structures as-is, which is
more verbose, but much more extensible, and a whole lot clearer in intent
aswell.
Since these are not particularly user facing macros, I opted not to include them
in `UPGRADING.md`, and removed them without prior deprecation.
Signed-off-by: Gergely Nagy <algernon@keyboard.io>