Lisk-sdk: Use channel instead of event emitter

[shuse2]

Expected behavior

Within module, it should consistently use channel instead of event emitter.
Event emitter can handle internal events within modules too.

Actual behavior

Event emitter was used when removing bus

Which version(s) does this affect? (Environment, OS, etc...)

2.2-

[shuse2]

This issue need to consider future impact on the modules which will be in the elements

[limiaspasdaniel]

@shuse2, regarding the ongoing BFT implementation, the way events are currently emitted is not consistent, for example EVENT_NEW_BLOCK is not emitted when receiving a block from the network passively and applying it.

I have an idea in mind to unify this behavior for example by emitting this in processBlock or similar, but using channels.

This is what it currently looks like on 2.0:

We also have to take into account EVENT_NEW_BROADHASH in the new BFT impl.

[pablitovicente]

Let's remember to have into account potential cases described in https://github.com/LiskHQ/lisk-sdk/issues/3539

[shuse2]

Closing because channel is now consistently use for external communication from the framework, and internally eventEmitter is used.