QtCreator: new MCU project template using the new .qmlproject MCU APIs

The template MCU project in QtCreator needs to be updated to include a .qmlproject with all the new properties and types defined in Qt for MCUs. 

The template .qmlproject should explicitly define all available properties, to make it easier for users to change these properties without having to look into the documentation for what is available. Properties could be split using comments into different logical categories.
Each property could also have a one-line comment briefly explaining what the property does.

The template CMakeLists also need to be updated to include the new .qmlproject file.

If the qmlprojectexporter feature is first released as a Tech Preview, Qt Creator should only offer to use it as an option, with an explicit warning about being not a stable feature.