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/ir.cpp

@@ -593,7 +593,7 @@ static void decodeIRJson(uint32_t code)
         decBrightness();
       } else if (cmdStr.startsWith(F("!presetF"))) { //!presetFallback
         uint8_t p1 = fdo["PL"] | 1;
-        uint8_t p2 = fdo["FX"] | random8(strip.getModeCount() -1);
+        uint8_t p2 = fdo["FX"] | hw_random8(strip.getModeCount() -1);
         uint8_t p3 = fdo["FP"] | 0;
         presetFallback(p1, p2, p3);
       }