Retire our copies of some MSBuild types

```
xamarin-macios/tests/common/BinLog.cs(76,10): error CS0433: The type 'TargetSkipReason' exists in both 'Microsoft.Build.Framework, Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' and 'StructuredLogger, Version=2.1.0.0, Culture=neutral, PublicKeyToken=d4c7181801cb6448' [xamarin-macios/tests/msbuild/Xamarin.MacDev.Tests/Xamarin.MacDev.Tests.csproj]
```