Comparison: Improve the text for unknown failures' compressed results

Let's consider the following report:

Possible new issues

Here are the unknown changes that may have been introduced in IGTPW_5853:

IGT changes

Possible regressions

    igt@gem_tiled_blits@basic:
        fi-tgl-y: PASS -> FAIL +3 similar issues

Here, +3 similar issues actually means "+3 other tests failing with the same status". @tsa proposed to replace the text with "+3 other tests", but I would like to come up with something less ambiguous here.