Fix Fail -> UnexpectImprovement(Skip) transition
We were looking to the line number of different files, let's just add
the new skip expectation to the skiplist and notify, via fixed_tests
list that the fail list should be updated as well.
This MR fixes the problems found during this uprev: https://gitlab.freedesktop.org/gfx-ci/ci-uprev/-/jobs/54965522