CLI: replace old .NET Framework manifest-signing (ClickOnce) code with dotnet-mage

[dtivel]

We shouldn't own copies of .NET Framework manifest-signing code (e.g.: mansign.cs and mansign2.cs). We should delete all this code and move to a solution that does this for us.

See https://learn.microsoft.com/en-us/visualstudio/deployment/clickonce-deployment-dotnet?source=recommendations&view=vs-2022#mageexe.

dotnet-mage is the newest incarnation of mage.exe. We should talk with that team about integrating it into sign CLI.

CC @clairernovotny