Please change MSIX package name to Microsoft.WindowsAppRuntime.Major.Minor.Patch

[stevenbrix]

Since the current package names are only Major.Minor, Patch builds can come out and break apps. Since MSIX packages don't support pinning, this is the next best thing to ensure that folks are on stable builds. It isn't the worst thing in the world to have multiple different versions installed on the machine. And while this may mean a machine has 1.5.0, 1.5.1, 1.5.2, etc. installed, it isn't guaranteed to. However, if us app developers all can't be protected from random updates breaking us, we'll all ship self-contained, which guarantees that there will be 1 copy of the windows app sdk installed on the machine per app that uses it