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/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,