Improvement to unsupported backward OpInfo test

[walterddr]

Unsupported backward OpInfo test added in #59455 is used to ensure that backward opinfo test are properly enabled instead of just being skipped. Follow up

• to_sparse is not checked error raise properly, see: [BE] unsupported backward failing on single sample #59455 (comment)
• supported_backward() still have several skips, needs to be cleaned up.
• handle non-tensor outputs properly.

cc @mruberry @VitalyFedyunin @walterddr

[walterddr]

this is addressed in #60157