[BH-861] Cleanup Application split - part I

1. Prepare Pure and Bell specific `Application`
   classes and add them to `app` target:

- `products/BellHybrid/apps/Application.cpp`
- `products/PurePhone/apps/Application.cpp`

2. Update `CMakeLists.txt` files.
3. Move `ApplicationBell` implementation to Bell-specific
   `Application` class and remove `ApplicationBell` files.
4. Change Bell apps parent classes from `ApplicationBell`
  to Bell-specific `Application` class.
5. Rename `Application` to `ApplicationCommon` in the rest of the files.

module-apps/application-notes/model/NotesRepository.cpp

@@ -12,7 +12,7 @@
 
 namespace app::notes
 {
-    NotesDBRepository::NotesDBRepository(Application *application)
+    NotesDBRepository::NotesDBRepository(ApplicationCommon *application)
         : app::AsyncCallbackReceiver{application}, application{application}
     {}