Refactoring to PolledTimeout or optimistic_yield on the grounds that these are not wait loops on slow input.

cores/esp8266/HardwareSerial.cpp

@@ -146,7 +146,6 @@ unsigned long HardwareSerial::detectBaudrate(time_t timeoutMillis)
         if ((detectedBaudrate = testBaudrate())) {
           break;
         }
-        yield();
         delay(100);
     }
     return detectedBaudrate;

cores/esp8266/debug.cpp

@@ -54,7 +54,7 @@ void hexdump(const void *mem, uint32_t len, uint8_t cols)
         }
         src += linesize;
         len -= linesize;
-        yield();
+        optimistic_yield(10000);
     }
     os_printf("\n");
 }