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/bus_manager.cpp

@@ -420,7 +420,9 @@ BusNetwork::BusNetwork(BusConfig &bc) : Bus(bc.type, bc.start, bc.autoWhite) {
 void BusNetwork::setPixelColor(uint16_t pix, uint32_t c) {
   if (!_valid || pix >= _len) return;
   if (hasWhite()) c = autoWhiteCalc(c);
+#if !defined(WLEDMM_FASTPATH) // WLEDMM expensive operation
   if (_cct >= 1900) c = colorBalanceFromKelvin(_cct, c); //color correction from CCT
+#endif
   uint16_t offset = pix * _UDPchannels;
   _data[offset]   = R(c);
   _data[offset+1] = G(c);