Add option to show reference output in check results

[agoscinski]

Right now assert allclose output is like this

assert_numpy_allclose failed for
|   x: array([0.        , 3.14159265, 6.28318531])
| > output 0: [ 1. -1.  1.]
| Output is not close to reference absolute difference is 3.0, relative difference is 3.0.

For assert_equal it works because it is in the message

assert_equal failed for
|   x: 2
| > output 0: 2
| Expected 4 but got 2.

But it would be nice if the reference output can be shown like this

assert_numpy_allclose failed for
|   x: array([0.        , 3.14159265, 6.28318531])
| > output 0: [ 1. -1.  1.]
| > ref output 0: [0., 0., 0.]
| Output is not close to reference absolute difference is 3.0, relative difference is 3.0.