updates for mdev PIO config

- updated mdev config, to use latest arduinoFFT, plus threadsafe LittleFS, plus default to 80Mhz flash speed.
- re-introducing the preset saving fix from SR WLED. Still I don't believe that upstream got that corrected properly.

wled00/presets.cpp

@@ -38,6 +38,18 @@ void handlePresets(bool force)
   uint8_t core = 1;
   #ifdef ARDUINO_ARCH_ESP32
   core = xPortGetCoreID();
+	// begin WLEDSR specific
+	//      loopTask (arduino main loop) sometimes runs on core #1
+	if ((core == 1) && (strncmp(pcTaskGetTaskName(NULL), "loopTask", 8) == 0)) {
+		DEBUG_PRINTF("[applyPreset] called from loopTask on core %d; forcing core = 0\n", (int)core); 
+		core = 0;
+	}
+	//      async_tcp (network requests) sometimes runs on core #0
+	if ((core == 0) && (strncmp(pcTaskGetTaskName(NULL), "async_tcp", 9) == 0)) {
+		DEBUG_PRINTF("[applyPreset] called from async_tcp on core %d; forcing core = 1\n", (int)core); 
+		core = 1;
+	}
+	// end WLEDSR specific
   #endif
   //only allow use of fileDoc from the core responsible for network requests (AKA HTTP JSON API)
   //do not use active network request doc from preset called by main loop (playlist, schedule, ...)