feat: Implement Live Session Resumption

Previous implementation doesn't pass the actual handle to server. Now we cache the handle and pass it over when reconnection happens.

To enable:
    run_config = RunConfig(
        session_resumption=types.SessionResumptionConfig(transparent=True)
    )

PiperOrigin-RevId: 791308462

src/google/adk/models/gemini_llm_connection.py

@@ -219,6 +219,13 @@ class GeminiLlmConnection(BaseLlmConnection):
             for function_call in message.tool_call.function_calls
         ]
         yield LlmResponse(content=types.Content(role='model', parts=parts))
+      if message.session_resumption_update:
+        logger.info('Redeived session reassumption message: %s', message)
+        yield (
+            LlmResponse(
+                live_session_resumption_update=message.session_resumption_update
+            )
+        )
 
   async def close(self):
     """Closes the llm server connection."""

src/google/adk/models/google_llm.py

@@ -289,6 +289,7 @@ class Gemini(BaseLlm):
         ],
     )
     llm_request.live_connect_config.tools = llm_request.config.tools
+    logger.info('Connecting to live with llm_request:%s', llm_request)
     async with self._live_api_client.aio.live.connect(
         model=llm_request.model, config=llm_request.live_connect_config
     ) as live_session:

src/google/adk/models/llm_response.py

@@ -89,6 +89,11 @@ class LlmResponse(BaseModel):
   usage_metadata: Optional[types.GenerateContentResponseUsageMetadata] = None
   """The usage metadata of the LlmResponse"""
 
+  live_session_resumption_update: Optional[
+      types.LiveServerSessionResumptionUpdate
+  ] = None
+  """The session resumption update of the LlmResponse"""
+
   @staticmethod
   def create(
       generate_content_response: types.GenerateContentResponse,