Move setSlowWrite call from menuPortSelector to serial.open

Remove useless ESP32 slow write check that didn't disable it
Disable slow write on ESP32 as there's flow control

core/serial.js

@@ -142,6 +142,7 @@ To add a new serial device, you must add an object to
   };
 
   var openSerial=function(serialPort, connectCallback, disconnectCallback) {
+    Espruino.Core.Serial.setSlowWrite(true); // force slow write to ensure things work ok - we may disable this when versionChecker figures out what board/version we use
     return openSerialInternal(serialPort, connectCallback, disconnectCallback, 5);
   }
 

plugins/versionChecker.js

@@ -60,9 +60,10 @@
           (env.CONSOLE=="USB"||env.CONSOLE=="Bluetooth"||env.CONSOLE=="Telnet")) {
         console.log("Firmware >1.43 supports faster writes over USB");
         Espruino.Core.Serial.setSlowWrite(false);
-      } else if (vCurrent >= 2.18 && env.BOARD=="ESP32" && env.CONSOLE=="Serial1") {
-        console.log("Firmware >=2.18 on ESP32 supports flow control");
-        Espruino.Core.Serial.setSlowWrite(true);
+      } else {
+        // setSlowWrite(true) called in Serial.open so is the default
+        if ( Espruino.Core.Serial.isSlowWrite()) // not disabled already?
+          console.log(`Note: Uploads may be slow. Use SERIAL_THROTTLE_SEND/'Throttle Send' option to disable throttling at the expense of unreliable uploads on some boards.`);
       }
 
       if (env.info!==undefined &&