Update EspSoftwareSerial to release 5.0.0. (#5965)

* Update EspSoftwareSerial to release 5.0.0.

(Includes half-duplex patch for SerialStress.ino)

* Updated EspSoftwareSerial to allow Platformio builds that lack defaults for RX/TX defines.

Author: dok-net

libraries/SoftwareSerial

@@ -74,6 +74,7 @@ void setup() {
   // so we can still log to the regular usbserial chips
   SoftwareSerial* ss = new SoftwareSerial(3, 1);
   ss->begin(SSBAUD);
+  ss->enableIntTx(false);
   logger = ss;
   logger->println();
   logger->printf("\n\nOn Software Serial for logging\n");