ARM - Initial backlight support (#6487)
* Move AVR backlight to own file, add borrowed ARM implementation
* Tiny fix for backlight custom logic
* Remove duplicate board from rebase
* Fix f303 onekey example
* clang-format
* clang-format
* Remove backlight keymap debug
* Initial pass of ARM backlight docs
* Initial pass of ARM backlight docs - resolve todos
* fix rules validation logic
* Add f072 warning
* Add f072 warning
* tidy up breathing in backlight keymap
* tidy up breathing in backlight keymap
* add missing break to backlight keymap
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