Python: [BREAKING]: removed display_name, renamed context_providers, middleware and AggregateContextProvider (#3139)

* removed display_name, renamed context_providers, middleware and AggregateContextProvider

* fixes

* fixed test

* testfix

* removed mistakenly put back test

* updated new test

* rename middlewares to middleware

* middleware fixes

python/samples/getting_started/middleware/chat_middleware.py

@@ -146,7 +146,7 @@ async def class_based_chat_middleware() -> None:
             name="EnhancedChatAgent",
             instructions="You are a helpful AI assistant.",
             # Register class-based middleware at agent level (applies to all runs)
-            middleware=InputObserverMiddleware(),
+            middleware=[InputObserverMiddleware()],
             tools=get_weather,
         ) as agent,
     ):
@@ -168,7 +168,7 @@ async def function_based_chat_middleware() -> None:
             name="FunctionMiddlewareAgent",
             instructions="You are a helpful AI assistant.",
             # Register function-based middleware at agent level
-            middleware=security_and_override_middleware,
+            middleware=[security_and_override_middleware],
         ) as agent,
     ):
         # Scenario with normal query
@@ -226,7 +226,7 @@ async def run_level_middleware() -> None:
         print(f"User: {query}")
         result = await agent.run(
             query,
-            middleware=security_and_override_middleware,
+            middleware=[security_and_override_middleware],
         )
         print(f"Response: {result.text if result.text else 'No response'}")