Run perf tests on demand

[DifferentialOrange]

After #364, perf tests length is ~1h10m. One must wait till perf tests succeed each time to get an ok from test CI workflow. On the other hand, we don't really monitor performance changes on each patch (and maybe won't ever do since GitHub runners are small virtual machines, not suited for performance tests). It makes sense to run them only with specific label or on a workflow dispatch trigger.