Reorganize mysensors (#15123)

* Move mysensors.py to package

* Move mysensors component to package

* Split code into multiple modules.

* Update coveragerc

homeassistant/components/binary_sensor/mysensors.py

@@ -29,7 +29,8 @@ async def async_setup_platform(
         async_add_devices=async_add_devices)
 
 
-class MySensorsBinarySensor(mysensors.MySensorsEntity, BinarySensorDevice):
+class MySensorsBinarySensor(
+        mysensors.device.MySensorsEntity, BinarySensorDevice):
     """Representation of a MySensors Binary Sensor child node."""
 
     @property