RGB_
* Remove deprecated `RGB_` and Mouse keycodes * Update old mouse keycodes, 0-9/A-M * Update old mouse keycodes, N-Z & layouts * Missed some stuff
* Separate RGBLight/RGB Matrix keycode handling * Remove `_DISABLE_KEYCODES` handling * Update RGB Matrix keycode docs * Update underglow keycodes for previously migrated boards * Update keycodes for boards with custom handling * Fix typos * Fix bad merge