A d3d12 test seems excessive
I don't think we should keep a particularly high barrier on adding d3d12 tests. It would be nice to move as many as possible of them to the shader runner to save on boilerplate (and to make the shader runner language more powerful so that more tests can be converted), but in the meantime I don't think we want to give up on d3d12 tests because they're too many or because only some features can be tested there.