Add explicit history Icon to open the history panel + new conversation

[azaylamba]

We are using tools drawer of AppLayout for displaying user session history. The icon for tools drawer is Info icon which does not represent history, so end user might find it inconvenient to locate the session history. The icon is not customizable intentionally as mentioned here.

We should use secondary panels like Drawer for displaying session history.

[bigadsoleiman]

Possibly add a new button to create a new session from https://github.com/aws-samples/aws-genai-llm-chatbot/issues/283