Add ReportFinalizer handler to allow manipulation of final data for report generation

[AntyaDev]

Context:

• Implement Step.RunHidden to not show a step in the report #674
• Add a Hidden Step support #689

After deep investigation, we found that this task with hidden steps for HTML reports can be implemented via a more general approach based on filtering final stats data before the report generation.

• Add C#, F# API for NBomberRunner:

NBomberRunner
    .RegisterScenarios(scenario)
    .WithReportFinalizer(data =>
    {
        var scn = data.GetScenarioStats("scenario");
        scn.StepStats = scn.StepStats.Where(x => x.StepName != "hidden").ToArray();
        return data;
    })
    .Run();

• In case of an exception, the NBomber should log it without breaking the flow and return the default value.
• Add integration tests