Enable Qt modules to install Qt Creator/ Qt design Studio Project templates

For the Qt Quick 3D module, we'd like to introduce a Qt Creator template for Quick 3D Xr projects. (this also applies to Qt Design Studio) Instead of maintaining this in the Qt Creator repo and installing it for all Qt Creator users, it makes sense that it is maintained in the module that supports it and is only available once users have installed that module. This also means templates can be released in sync with the modules they are for.

Once this is implemented and tested for Quick 3d, it would make sense to manage all templates this way.