Prefer csproj method for InternalsVisibleTo

[lloydkevin]

https://learn.microsoft.com/en-us/dotnet/core/project-sdk/msbuild-props#internalsvisibleto

This way, you can skip the AssemblyInfo.cs creation.

Also, this might work:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <InternalsVisibleTo Include="$(AssemblyName).Tests" />
  </ItemGroup>
</Project>