Prevent SD access from resetting ESP32 (#16690)

Marlin/src/sd/SdVolume.cpp

@@ -291,6 +291,16 @@ int32_t SdVolume::freeClusterCount() {
       for (uint16_t i = 0; i < n; i++)
         if (cacheBuffer_.fat32[i] == 0) free++;
     }
+    #ifdef ESP32
+      // Needed to reset the idle task watchdog timer on ESP32 as reading the complete FAT may easily 
+      // block for 10+ seconds. yield() is insufficient since it blocks lower prio tasks (e.g., idle).
+      static millis_t nextTaskTime = 0;
+      const millis_t ms = millis();
+      if (ELAPSED(ms, nextTaskTime) {
+        vTaskDelay(1);            // delay 1 tick (Minimum. Usually 10 or 1 ms depending on skdconfig.h)
+        nextTaskTime = ms + 1000; // tickle the task manager again in 1 second
+      }
+    #endif // ESP32
   }
   return free;
 }