Port EventStream subscriptions

[cpx86]

In Go you can replace the default subscriber for deadletter and supervision events.

See e.g.:
https://github.com/AsynkronIT/protoactor-go/blob/dev/actor/options.go
https://github.com/AsynkronIT/protoactor-go/blob/dev/actor/deadletter.go

[tomliversidge]

Go also has a predicate to allow filtering of messages?

https://github.com/AsynkronIT/protoactor-go/blob/dev/eventstream/eventstream.go#L85
https://github.com/AsynkronIT/protoactor-go/blob/dev/eventstream/eventstream.go#L69

I've no experience of Go, but I'm presuming this is more than just filtering by type that we have in .net by using generics. i.e. a subscriber can subscribe to an event type and include a predicate to filter those types by?

[rogeralsing]

In Go, the WithPredicate simply wraps the subscriber func inside a predicate.
We can do the same with the .NET Subscribe(Action<T> action)

Closing as we have the bits we need here. we can re-open if further requirements arise