flakefinder: highlight tests with non-deterministic outcomes

[dhiller]

Is your feature request related to a problem? Please describe:
Flakefinder report currently shows all tests that were failing on any run. It doesn't highlight specifically a flaky run, which is two builds on the same commit id.

Describe the solution you'd like:
When the same test has non-deterministic outcomes on two builds for the same lane and commit id we want to highlight it in the report

Describe alternatives you've considered:

Additional context:

• Example PR history: https://prow.ci.kubevirt.io/pr-history/?org=kubevirt&repo=kubevirt&pr=13630

/sig ci
/area flakefinder