Revert "Migrate test projects to MSTest.Sdk"

[dfederm]

Reverts #99

Broken official builds. Something about strong naming. Ugh.

D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed: Tests failed:  [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed: Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'Microsoft.MSBuildCache.Repack.Tests, Version=0.1.0.0, Culture=neutral, PublicKey***=6702f781b82f5f3b' or one of its dependencies. Strong name validation failed. (Exception from HRESULT: 0x8013141A) ---> System.Security.SecurityException: Strong name validation failed. (Exception from HRESULT: 0x8013141A) [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed:    --- End of inner exception stack trace --- [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed:  [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed: === COMMAND LINE === [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed: D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe --internal-msbuild-node testingplatform.pipe.9eac05d720244ab9a58898088e82d1f8  [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed:  [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Repack.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Repack.Tests.exe : error run failed:  [D:\a\_work\1\s\src\Repack.Tests\Microsoft.MSBuildCache.Repack.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed: Tests failed:  [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed: Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'Microsoft.MSBuildCache.Common.Tests, Version=0.1.0.0, Culture=neutral, PublicKey***=6702f781b82f5f3b' or one of its dependencies. Strong name validation failed. (Exception from HRESULT: 0x8013141A) ---> System.Security.SecurityException: Strong name validation failed. (Exception from HRESULT: 0x8013141A) [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed:    --- End of inner exception stack trace --- [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed:  [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed: === COMMAND LINE === [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed: D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe --internal-msbuild-node testingplatform.pipe.4298a9180474405fad9876f4444ae58a  [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed:  [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
D:\a\_work\1\s\src\Common.Tests\bin\x64\Release\net472\Microsoft.MSBuildCache.Common.Tests.exe : error run failed:  [D:\a\_work\1\s\src\Common.Tests\Microsoft.MSBuildCache.Common.Tests.csproj::TargetFramework=net472]
    0 Warning(s)
    2 Error(s)