Add support for SpiNorFlash and FS (#30)

The external SPI flash is implemented as a 4MB on the local filesystem.
This allows the FS (littleFS) and settings to work properly.

Remove the simulated `FS.h` and `FS.cpp`, because we can now use
the files from InfiniTime directly as the heavy lifting is done in the simulated
`SpiNorFlash.h` and cpp files.

`SpiNorFlash.h` provides read and write functions with `uint8_t` buffer, but
`fs::fstream` expects `char` buffer. Use `reinterpret_cast` and check if by
any chance the `char` type on a platform is implemented with more
than one byte. Then the `reinterpret_cast<char *>(buffer)` would change the
meaning of the `size` parameter, which could lead to garbage data.

Co-authored-by: Reinhold Gschweicher <pyro4hell@gmail.com>

main.cpp

@@ -224,7 +224,7 @@ Pinetime::Drivers::Spi lcdSpi {spi, Pinetime::PinMap::SpiLcdCsn};
 Pinetime::Drivers::St7789 lcd {lcdSpi, Pinetime::PinMap::LcdDataCommand};
 
 Pinetime::Drivers::Spi flashSpi {spi, Pinetime::PinMap::SpiFlashCsn};
-Pinetime::Drivers::SpiNorFlash spiNorFlash {flashSpi};
+Pinetime::Drivers::SpiNorFlash spiNorFlash {"spiNorFlash.raw"};
 
 // The TWI device should work @ up to 400Khz but there is a HW bug which prevent it from
 // respecting correct timings. According to erratas heet, this magic value makes it run
@@ -252,7 +252,7 @@ Pinetime::Controllers::Ble bleController;
 Pinetime::Controllers::HeartRateController heartRateController;
 Pinetime::Applications::HeartRateTask heartRateApp(heartRateSensor, heartRateController);
 
-Pinetime::Controllers::FS fs; // {spiNorFlash};
+Pinetime::Controllers::FS fs {spiNorFlash};
 Pinetime::Controllers::Settings settingsController {fs};
 Pinetime::Controllers::MotorController motorController {};
 
@@ -837,6 +837,8 @@ int main(int argc, char **argv)
   /*Initialize the HAL (display, input devices, tick) for LVGL*/
   hal_init();
 
+  fs.Init();
+
   // initialize the core of our Simulator
   Framework fw(fw_status_window_visible, 240,240);