Overhaul events to use EventHandler

[gigajuwels]

This PR deprecates the old style source.On(eventId, ...) style event system, with the standard C# EventHandler system. The old event system is still partially supported (but will be removed).

The only events that remain using the EventEmitter.NET system are events that have a dynamic eventId or a generic type as the event parameter

[skibitsky]

Thanks! This PR is very welcomed! However, I'd suggest to completely remove EventEmitter.NET to have consistent approach towards events and avoid external dependency.

[gigajuwels]

We can remove the obsolete events, however we will still need EventEmitter.NET to execute the remaining dynamic events. See here and here for examples where a normal EventHandler would not suffice. A dynamic event is an event that

1. Has a dynamic event id / name. The event id/name is not known at compile time, but only known at runtime (i.e a request/response method, here)
2. Has a generic argument type T. Example can be seen here

The EventEmitter.NET library is the now removed WalletConnectSharp.Events library. This kind of library is better placed as its own thing outside WalletConnect, so it does not need to manage this kind of complex dynamic dispatch logic.