Provide reference to BrightnessController in DisplayApp

For the simulator I need a way to get to the brightnessController object
and handle the set brightness-levels accoringly.

This is done by the constructor expecting a brightnessController object
instead of initializing one itself

src/displayapp/DisplayApp.cpp

@@ -97,6 +97,7 @@ DisplayApp::DisplayApp(Drivers::St7789& lcd,
                        Pinetime::Controllers::MotionController& motionController,
                        Pinetime::Controllers::TimerController& timerController,
                        Pinetime::Controllers::AlarmController& alarmController,
+                       Pinetime::Controllers::BrightnessController& brightnessController,
                        Pinetime::Controllers::TouchHandler& touchHandler)
   : lcd {lcd},
     lvgl {lvgl},
@@ -112,6 +113,7 @@ DisplayApp::DisplayApp(Drivers::St7789& lcd,
     motionController {motionController},
     timerController {timerController},
     alarmController {alarmController},
+    brightnessController {brightnessController},
     touchHandler {touchHandler} {
 }