fix: include rewind_before_invocation_id in VertexAiSessionService.append_event#4978

yuting0624 wants to merge 4 commits intogoogle:maingoogle/adk-python:mainfrom

yuting0624:fix/4930-vertex-session-rewindyuting0624/adk-python:fix/4930-vertex-session-rewindCopy head branch name to clipboard