Clean up [ConditionalFact(typeof(Environment), nameof(Environment.Is64BitProcess))]

[tannergooding]

It was suggested that creating explicit attributes for the various cases (Such as Onnx, TensorFlow, LightGBM, etc) may be a better long term solution to manage these tests across the various platforms.

See #1008 (comment) for more details.

[mareklinka]

Hi there. I started looking into this and came up with the following list of attributes that would be necessary:

1. TensorFlow
2. Onnx
3. LightGBM
4. .NET Core < 3.0 || not Core
5. MatrixFactorization
6. Environment = x64 (e.g. where x86 output differs from expected baseline, TestCommandBase:841)
7. x64 && (.NET Core < 3.0 || not Core)
8. NotFullFramework