Bug: ignoreFailed tests shouldn't be counted when calculating systematic failures

[NiccoloFei]

In compute_systematic_failures_on_metric() we are counting ignoreFailed tests for the total runs, which makes it impossible to have systematic failures by_k8s / by_postgres / by_platform given that failures == runs is always going to be False.

Note: There's only one case in which we could trigger systematic failures by_k8s / by_postgres / by_platform at the moment, and that's in case the Ginkgo suite didn't run at all (for example because the Cluster creation or any step that precedes the start of the e2e failed). In that case you would have a single failed Open Ginkgo report artifact which would make systematic failures by_k8s / by_postgres / by_platform properly trigger.

To fix this we should avoid including ignoreFailed tests in the total runs when calculating systematic failures.