Refactor component gRPC clients

[rvolosatovs]

Clients should be refactored to work in the same way as monitorclient

• [ ] broker
• [x] ~handler~
• [ ] router
• [x] ~discovery~

@htdvisser do handler and network server belong here or should they be removed at all?

[htdvisser]

I think we should only create overlays for streams, as those can be complicated to use. Unary calls do not need overlays, so we probably should get rid of those in discovery and handler(manager). As far as I know, there isn't anything in networkserver

[rvolosatovs]

my bad, should have been discovery, not network server

[htdvisser]

Abandoning this in v2