feat: add EventSource enum and optimize event processing threads

- Introduce EventSource enum (Grpc, Shred) for better event source management
- Refactor start_block_processing_thread to conditionally spawn threads based on source type
- Update callers to specify event source type

src/streaming/shred_stream.rs

@@ -40,6 +40,7 @@ impl ShredStreamGrpc {
         let mut event_processor =
             EventProcessor::new(self.metrics_manager.clone(), self.config.clone());
         event_processor.set_protocols_and_event_type_filter(
+            super::common::EventSource::Shred,
             protocols,
             event_type_filter,
             self.config.backpressure.clone(),