Fix binary protocol with one serial port (#13270)

- The `sdcard.transfer_port` variable is Marlin's internal serial port index, not the physical serial port number.
- Added packet number to "ok" response so hosts don't need to wait for the ACK.
- Renamed feature to `BINARY_FILE_TRANSFER`, as the speed up is only consequential to the ability to transfer binaries over serial.

Marlin/src/gcode/sdcard/M20-M30_M32-M34_M524_M928.cpp

@@ -175,7 +175,7 @@ void GcodeSuite::M27() {
  */
 void GcodeSuite::M28() {
 
-  #if ENABLED(FAST_FILE_TRANSFER)
+  #if ENABLED(BINARY_FILE_TRANSFER)
 
     bool binary_mode = false;
     char *p = parser.string_arg;