Закрыть тудушку в LoadingService и написать тесты

[VeselAbaya]

It's needed to use stack inside that service, to hide loading only when All pending activities resolves
e.g. on() --> -100ms- -100ms- -100ms- -100ms- --> off() (1)
on() --> -100ms- -100ms- --> off() (2)
in such situation after off() call on (2) row in LoadingService#active$ will be false in spite of pending request that we started on (1) row