screens: Remove displayapp parameter from screen

The DisplayApp class isn't used in the Screen base class and most
screens, so requiring it is pointless.

In this commit, DisplayApp pointers were added to screens which use it
and the explicit Screen constructor was removed in those screens.

src/displayapp/screens/Label.h

@@ -10,7 +10,7 @@ namespace Pinetime {
 
       class Label : public Screen {
       public:
-        Label(uint8_t screenID, uint8_t numScreens, DisplayApp* app, lv_obj_t* labelText);
+        Label(uint8_t screenID, uint8_t numScreens, lv_obj_t* labelText);
         ~Label() override;
 
       private: