speed optimisations, fix for restoreColorLossy, code cleanup (#4895)

- speed optimization in color_add, PS fast_color_add and blur functions
- applying more bit and shift manipulation tricks to squeeze out just a bit more speed on color manipulation functions.
- Optimization on blur is based on work by @blazoncek
- Renamed PS fast_color_add() to fast_color_scaleAdd()

wled00/const.h

@@ -682,4 +682,6 @@ static_assert(WLED_MAX_BUSSES <= 32, "WLED_MAX_BUSSES exceeds hard limit");
   #define IRAM_ATTR_YN IRAM_ATTR
 #endif
 
+#define WLED_O2_ATTR __attribute__((optimize("O2")))
+
 #endif