(feat) Dev APIs: Add lifecycle events with AGUI protocol (#10780)

Proof of Concept: Adding lifecycle events.

Added AGUI events to vertices and the graph. Created Decorator to add observability to Langflow workflows. TODO: Unit tests, feature gating to nullify impact in current production code paths.

Added unit tests for lifecycle_events. Refraining from using event_manager for now since this capability is goig to stay dormant until APIs are ready for streaming.

Added unit tests for before_callback_event and after_callback_event in graph and vertex classes.

Co-authored-by: Debojit Kaushik <[email protected]>