Tweak the Christmas animation effect to be less harsh on the eyes (#7648)

* Tweak the Christmas animation effect to be less harsh on the eyes

* Further improve the tweaked Christmas animation code

- Use constants where it makes sense
- Instead of complicated math, use a static variable to keep track if it's animating from or to red
- Don't use pow (but a simple macro instead)
- Using floating point math is necessary for the fraction in the cubic bezier function to work

* Update docs for the tweaked Christmas animation effect

* Further improve memory usage

- Don't use floats, but 32 bit ints instead (where needed)
- Replace limits.h with constant

* Fix typo

quantum/rgblight.h

@@ -142,7 +142,7 @@ enum RGBLIGHT_EFFECT_MODE {
 #    endif
 
 #    ifndef RGBLIGHT_EFFECT_CHRISTMAS_INTERVAL
-#        define RGBLIGHT_EFFECT_CHRISTMAS_INTERVAL 1000
+#        define RGBLIGHT_EFFECT_CHRISTMAS_INTERVAL 40
 #    endif
 
 #    ifndef RGBLIGHT_EFFECT_CHRISTMAS_STEP