Update MAUI example for .NET 9

[bobwhitten]

The current example is for .NET 6, and the Microsoft.Identity.Client has moved a long way since then. I can find NO good sample for my need, which is simple:

Port my working Xamarin iOS code to my MAUI migrated app to allow my users to automatically put a file into a folder in their OneDrive.

My app creates test reports, sometimes as many as 20 per day, and this method allows the user to upload them with a single button press to a pre-selected folder. While they could do this doing "share", it is many more steps and is error-prone. It currently uses the nuget Microsoft.Identity.Client 4.60.4 for authentication with a redirect of the style "msauth://com.mycompany.MyApp"

It would be great to have an up-to-date example.