Use OMG.Bus module as argument instead of calling it directly

[pgebal]

In some modules we call OMG.Bus functions directly and in others, for example OMG.Eth.EthereumHeightMonitor we pass the OMG.Bus module as a parameter and call functions using apply. Let's decide on parameter approach wherever we use the event bus.

As @pnowosie suggested: Or it might be the opposite: we should pass the bus module as a param everywhere and mock more on tests as we're moving from integration tests to unit + cabbage

WDYT @InoMurko ❓

Originally posted by @pnowosie in https://github.com/omisego/elixir-omg/pull/1441