[FEATURE] Ability to filter callback / iterator messages

[MaDDoGo]

Problem Statement

I would like the ability to filter events for easier consumption

Proposed Solution

Add a parameter to agent to filter events (all, messages, blocks for example)

Use Case

With this in place, code will be simpler

if "delta" in event:

or

if "message" in event:

as it will yield only the wanted events

Alternatives Solutions

No response

Additional Context

No response

[MaDDoGo]

This could be a good addition to #242 by yielding type safe(r) events (I don't even know if this kind of method overloading is possible with type hints, but could be helpful)