Python: Add Python feature lifecycle decorators for released APIs (#4975)

* Add Python feature lifecycle decorators

Introduce reusable experimental and release-candidate decorators for released packages, migrate the Skills APIs to the new staged metadata and warning system, and add lifecycle guidance plus samples.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix Python CI follow-ups

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address PR review feedback

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Preserve protocol runtime checks

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/packages/azure-ai/tests/test_azure_ai_client.py

@@ -76,8 +76,8 @@ def mock_project_client() -> MagicMock:
     mock_client.telemetry = MagicMock()
     mock_client.telemetry.get_application_insights_connection_string = AsyncMock()
 
-    # Mock get_openai_client method
-    mock_client.get_openai_client = MagicMock()
+    # AIProjectClient.get_openai_client() is a sync accessor, even on the aio client.
+    mock_client.get_openai_client = MagicMock(return_value=MagicMock())
 
     # Mock close method
     mock_client.close = AsyncMock()

python/packages/azure-ai/tests/test_provider.py

@@ -33,8 +33,8 @@ def mock_project_client() -> MagicMock:
     mock_client.telemetry = MagicMock()
     mock_client.telemetry.get_application_insights_connection_string = AsyncMock()
 
-    # Mock get_openai_client method
-    mock_client.get_openai_client = MagicMock()
+    # AIProjectClient.get_openai_client() is a sync accessor, even on the aio client.
+    mock_client.get_openai_client = MagicMock(return_value=MagicMock())
 
     # Mock close method
     mock_client.close = AsyncMock()