Refactor IEventReader interface to use generics

There are more reader interfaces and the only difference is type which is returned from next function.

public EventRecord next();

Using generics it is possible to create single IReader interface.

Locate IEventReader and the other reader interfaces, then compare their next() methods and return types. Determine the shared generic IReader shape from those interfaces; the refactor is done when the duplicate reader interfaces are replaced consistently and the project still builds.

Written by the indexing model from the issue text.