decouple cli/msp from each other. relocated non-msp code into

serial_common.c/h. decouple runtime_config from serial ports.  decouple
buzzer from serial ports.  decouple opening of the main serial port from
the msp code.  decouple serial rx providers from runtime_config.  rename
core_t to serialPorts_t since it only contained serial ports.  It's now
clear which files use serial ports based on the header files they
include.

src/mw.c

@@ -175,7 +175,7 @@ void annexCode(void)
         }
     }
 
-    serialCom();
+    handleSerial();
 
     if (!cliMode && feature(FEATURE_TELEMETRY)) {
         handleTelemetry();