some effect optimizations

* getpixelcolor: attribute pure - it reads memory, but does not write
* some optimizations for SEGMENT.blur() and SEGMENT.fadeToBlackBy()

* FX.c:pp remove double calls to blur() and fade_out()
* FX.cpp: SEGMENT.setUpLeds() added to effects, to enable LED buffering (safe some time because getPixelColor does not need to access NeopixelBus)

* a few other optimizations to safe time and avoid "expensive" operations
* set I2C bus speed to 400kHz (default is 100Khz)

* a few other small optimizations and tweaks
* pio: esp32 V4 builds use "patch5" toolchain version, which contains a few bugfixes especially for memory management.

wled00/overlay.cpp

@@ -88,7 +88,9 @@ void _overlayAnalogCountdown()
 }
 
 void handleOverlayDraw() {
+#if !defined(WLEDMM_FASTPATH) // WLEDMM expensive operation, and most usermods don't draw overlays
   usermods.handleOverlayDraw();
+#endif
   if (overlayCurrent == 1) _overlayAnalogClock();
 }