Python: [BREAKING] Move workflow to main package (#767)

* Move workflow to main package

* Remove workflow specific unit test config

* Remove workflow-specific version info

* Revert unintended telemetry changes

* Removed the obsolete packages/workflow/tests target

* Rename dir workflow to _workflow

* Fix test imports

python/samples/getting_started/telemetry/04-workflow.py

@@ -3,14 +3,14 @@
 import asyncio
 from typing import Any
 
-from agent_framework.telemetry import setup_telemetry
-from agent_framework.workflow import (
+from agent_framework import (
     Executor,
     WorkflowBuilder,
     WorkflowCompletedEvent,
     WorkflowContext,
     handler,
 )
+from agent_framework.telemetry import setup_telemetry
 from opentelemetry import trace
 from opentelemetry.trace import SpanKind
 from opentelemetry.trace.span import format_trace_id