ENH: testing: hiding assertion internals in pytest traceback

[prady0t]

Fixes #780

[lucascolley]

thanks Pradyot!

Perhaps you could give this a quick test @ntessore?

[lucascolley]

confirmed that the xpx.testing frames are skipped:

In [3]: xpt.assert_equal(np.asarray(0), np.asarray(1))
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
Cell In[3], line 1
----> 1 xpt.assert_equal(np.asarray(0), np.asarray(1))

    [... skipping hidden 2 frame]

File ~/ghq/github.com/data-apis/array-api-extra/.pixi/envs/dev/lib/python3.14/site-packages/numpy/testing/_private/utils.py:919, in assert_array_compare(comparison, x, y, err_msg, verbose, header, precision, equal_nan, equal_inf, strict, names)
    914         err_msg += '\n' + '\n'.join(remarks)
    915         msg = build_err_msg([ox, oy], err_msg,
    916                             verbose=verbose, header=header,
    917                             names=names,
    918                             precision=precision)
--> 919         raise AssertionError(msg)
    920 except ValueError:
    921     import traceback

AssertionError:
Arrays are not equal

Mismatched elements: 1 / 1 (100%)
Max absolute difference among violations: 1
Max relative difference among violations: 1.
 ACTUAL: array(0)
 DESIRED: array(1)