Migrate to .NET 6

[seesharprun]

This PR is to track work on the upgrade to .NET 6

A couple of comments:

• A lot of the Cosmos DB and Storage libraries are hilariously out-of-date. These will require some code rewrite to get working again
• It's tough to justify the effort to update the WPF front-end with MAUI/WINUI in it's current state. I also recommend investigating Prism to make the UI a bit easier to manage and update moving forward
• Once the console application is working, some thought should be put into adding the csproj properties required to turn the migration tool into a dotnet global tool
• The test projects will require some manual rework of their project files to fix MSTest

Status:

• [x] Used the migration assistant to move forward to .NET 6
• [ ] Get the entire solution to build successfully
• [ ] Get a successful run of the unit tests
• [ ] Test the console application
• [ ] Test the WPF application (optional)