backlight breathing overhaul (#2187)

backlight breathing overhaul (#2187)

* add breathing to bananasplit

* backlight breathing overhaul

* fix the backlight_tick thing.

* fix for vision_division backlight

* fix a few keymaps and probably break breathing for some weirdly set-up boards.

* remove BL_x keycodes because they made unreasonable assumptions

* some fixes for BL keycodes

* integer cie lightness scaling

* use cie lightness for non-breathing backlight and make breathing able to reach true max brightness