test: parametrize test_array_functions (#678)

test_array_functions now has 56 passing test cases and 1 expected failure (`array_slice` being the expected failure Ref #670).

test_array_function_flatten was broken out as a single test because it was an outlier in terms of test-input.

test_array_function_obj_tests had a different set of asserts, so was broken out for 5 test cases.

Ref #671