Investigate package identity for Qt applications on Windows

Some Windows APIs require a package identity for Windows applications in order to be used. Among these are APIs that we probably will need in the future (for example for QTBUG-94009
) so we should prepare that and perhaps add this package identity to Qt applications by default.
 
As written here granting a package identity to a desktop application can be done either by packaging it using MSIX or by creating a sparse MSIX package.
 
To build and register a sparse package that grants package identity to your desktop app, follow these steps.

1. Create a package manifest for the sparse package
2. Build and sign the sparse package
3. Add the package identity metadata to your desktop application manifest
4. Register your sparse package at run time

Let's investigate if this should be done by default for Qt applications on Windows and if cmake brings functionality to do so or which additions are needed.