Split SystemMonitor into h and cpp file and move the logging code of the
`Process` function into the cpp file.

Depending of the `configUSE_TRACE_FACILITY` define from
`src/FreeRTOSConfig.h` create either a "FreeRtosMonitor" or a
"DummyMonitor".

Make the `Process()` function non-const, as the FreeRtosMonitor changes
the member variable `lastTick`.

In `SystemTask.h` we then only need to use `SystemMonitor`, without
knowledge of the `configUSE_TRACE_FACILITY` define.

Apply a few changes that were requested in the PR during the review.

# Conflicts:
#	src/CMakeLists.txt
#	src/displayapp/Apps.h
#	src/displayapp/DisplayApp.cpp
#	src/displayapp/Messages.h
#	src/displayapp/screens/settings/Settings.cpp

# Conflicts:
#	src/CMakeLists.txt
#	src/displayapp/Apps.h
#	src/displayapp/DisplayApp.cpp
#	src/displayapp/Messages.h
#	src/displayapp/screens/settings/Settings.cpp

SystemTask.h included BatteryController.h, and BatteryController.h
included SystemTask.h. If unlucky the class SystemTask isn't created yet
when BatteryController wants to use it.

Fix that cyclic dependency by forward declaring the BatteryController
class and including it in the SystemTask.cpp file, where it is needed.

Remove unused includes. The firmware still compiles fine without the
includes.

The static_cast syntax requires brackets around the input variable. The
implementation worked because the used input are defines, which add the
missing brackets like the following:
```cpp
  #define GPIO_PIN_CNF_SENSE_Low (3UL)
```

Fix alarm on time change

Improved notification timeout