Allow to modify test-step's stop time after it's stopped by void stopStep()

[skif443]

Problem Our testing framework accumulates tests results during execution and then reports them in multiple ways (including Allure). Right now it's impossible to modify stop time of particular test step because void stopStep() method removes test-step's uuid after execution (storage.remove(uuid);).

To discuss Is it possible to stop removing test-step's uuid from storage after stopStep() execution or make this removal parameter-dependent?