Replace PRNG with hardware RNG (#4225)

Both ESP8266 and ESP32 have a hardware random register. This update makes use of that. It is slightly faster than the fastled variants but mostly it is truly random, even when the timing limitations stated in the datasheet are disregarded. Also saves a bit on code size.

- Replaced all random8() and random16() calls with new hw_random() versions
- Not replaced in FX where PRNG is required

wled00/wled.cpp

@@ -544,14 +544,8 @@ void WLED::setup()
 #endif
 
   // Seed FastLED random functions with an esp random value, which already works properly at this point.
-#if defined(ARDUINO_ARCH_ESP32)
-  const uint32_t seed32 = esp_random();
-#elif defined(ARDUINO_ARCH_ESP8266)
-  const uint32_t seed32 = RANDOM_REG32;
-#else
-  const uint32_t seed32 = random(std::numeric_limits<long>::max());
-#endif
-  random16_set_seed((uint16_t)((seed32 & 0xFFFF) ^ (seed32 >> 16)));
+  const uint32_t seed32 = hw_random();
+  random16_set_seed((uint16_t)seed32);
 
   #if WLED_WATCHDOG_TIMEOUT > 0
   enableWatchdog();