This new implementation of the weather feature provides a new BLE API and a new weather service.
The API uses a single characteristic that allows companion apps to write the weather conditions (current and forecast for the next 5 days).
The SimpleWeather service exposes those data as std::optional fields.
This new implementation replaces the previous WeahterService.
The API is documented in docs/SimpleWeatherService.md.
A list of "user applications" is built at compile time. It contains all the info needed to create the application at runtime (ptr to a create() function) and to display the app in the application menu. All applications declare a TypeTrait with these information.
When a new app must be loaded, DisplayApp first check if this app is a System app (in which case it creates it like it did before). If it's not a System app, it looks for the app in the list of User applications and creates it if it found it.
Those changes allow to more easily add new app and to select which app must be built into the firmware.
Switch to C++20 (and fix a few issues in SpiMaster.cpp and Watchdog.cpp.
