As you have guessed, most of these "unknown programs" are generated form Visual Studio when you deploy or debug UWP apps. And some of them are created by XAML Designer to provide synchronized Design view. These apps won't be listed in Apps & features. One possible way to find them is using PowerShell with the following command:
Get-AppxPackage | ? {$_.IsDevelopmentMode -eq $True}
This command works because all these "unknown programs" are installed in development mode.
And then if you want to uninstall them, you can add Remove-AppxPackage
command like:
Get-AppxPackage | ? {$_.IsDevelopmentMode -eq $True} | Remove-AppxPackage
After this there should be no "unknown programs" in CCleaner.