Bump TUnit from 1.80.0 to 1.81.0 - #62

* If a nuget's minimum target is net47, then the resulting TargetFrameworks should include net471, net472, and net48.

For example:

For best performance all frameworks from the lowest TargetFramework up to and including the newest one should be targeted. The newest is net48 for .NET Framework and net11.0 for .NET.

Projects that produce a nuget and consume Polyfill:

* If a nuget targets netstandard, then the resulting TargetFrameworks should also include the .NET Framework targets up to net48 and the .NET targets up to net11.0.

* If a nuget's minimum target is net8.0, then the resulting TargetFrameworks should include net9.0, net10.0, and net11.0.

* If a nuget's minimum target is net47, then the resulting TargetFrameworks should include net471, net472, and net48.

For example:

For best performance all frameworks from the lowest TargetFramework up to and including the newest one should be targeted. The newest is net48 for .NET Framework and net11.0 for .NET.