refactor(workflow): Simplify node runner metadata handling

Rename retry_count to attempt_count and remove redundant run_id assignments.

Change-Id: I907c024214729cc15c33ac29dbc03d36246aed3a

Author: boyangsvl

src/google/adk/workflow/_node_runner.py

@@ -440,8 +440,6 @@ def schedule_dynamic_node_fn(
         ):
           if not event.node_info.source_node_name:
             event.node_info.source_node_name = _source_node_name
-          if not event.node_info.parent_run_id:
-            event.node_info.parent_run_id = _parent_run_id
 
         if isinstance(event, Event) and event.output is not None:
           has_output = True

tests/unittests/workflow/test_dynamic_node_scheduler.py

@@ -80,7 +80,6 @@ def _make_event(
   event.partial = False
   event.node_info = MagicMock(spec=NodeInfo)
   event.node_info.path = path
-  event.node_info.run_id = run_id
   event.node_info.output_for = output_for
   event.long_running_tool_ids = set(interrupt_ids) if interrupt_ids else None
   event.content = None