Add support for quad color epaper

[tannewt]

highlight_color2 is now available for pixel value 0b11. Black is 0b00, white is 0b01 and highlight_color is 0b10.

Also add support for multibit values written with one command when color_command isn't provided.

[dhalbert]

Thanks! This looks fine -- I can't test.

I will mention a suggestion I made long ago, which is to put args to the C display constructors into a struct, so we can use named arguments, use 0 as default values, etc., instead of passing dozens of arguments.

Will there ever be displays with three highlight colors? Maybe eventually it should be an array.

[tannewt]

Will there ever be displays with three highlight colors? Maybe eventually it should be an array.

Yup, I was thinking about this as well.

I will mention a suggestion I made long ago, which is to put args to the C display constructors into a struct, so we can use named arguments, use 0 as default values, etc., instead of passing dozens of arguments.

Do we have a separate issue for this? Claude may be able to do it.

[dhalbert]

Do we have a separate issue for this? Claude may be able to do it.

I finally created one: #10528.