Handle duplicate packages in nuget cache (#1386)

[ChristophLindemann]

Resolves #1386

The NuGetPackageResolver class now handles that a NuGet package folder can contain multiple useless .nupkg files.

This is a workaround for a .NET SDK 8 problem (https://github.com/dotnet/sdk/issues/40528) introduced by https://github.com/dotnet/sdk/pull/33835.

I confirm that the pull-request:

• [x] Follows the contribution guidelines
• [x] Is based on my own work
• [x] Is in compliance with my employer

[werwolfby]

Hi @ChristophLindemann is duplicate of #1355?