improve stability of DDP via tcp_task (websockets)

* protect pixel buffer changes with critical section
* protect segment list modification with critical section
* make _isServicing and _triggered atomic (move out of packed bitarray)
* allow custom timeout for waitUntilIdle - DDP needs a longer timeout
* protect strip.show() and effect drawing functions with mutex, to prevent crashes

wled00/udp.cpp

@@ -162,9 +162,8 @@ void realtimeLock(uint32_t timeoutMs, byte md)
 
     if (strip.isServicing()) {
       USER_PRINTLN(F("realtimeLock() entering RTM: strip is still drawing effects."));
-      strip.waitUntilIdle();
+      strip.waitUntilIdle(350);
     }
-    strip.service(); // WLEDMM make sure that all segments are properly initialized
     busses.invalidateCache(true);
     // WLEDMM end