text: Title: New event to trigger when a tab is in view, not necessarily explicitly selected by the user
  Body: - [x] I have searched to see if a similar issue already exists.
  
  **Is your feature request related to a problem? Please describe.**  
  While `gr.Tab` as the `select` event, it is only triggered when a user explicitly _selects_ the tab. What if the tab is selected by default and the user only has to select that tab in order to return to that tab after navigating away from it? Another event, such as `focus` or `default_selected` will be a good idea.
  
  **Describe the solution you'd like**  
  Support a new event for tabs that is triggered when the tab is in view, not necessarily because the user selected it.
  
  **Additional context**  
  To see what I mean, select the "Pydantic entity profiles" tab https://huggingface.co/spaces/anirbanbasu/gradio-experiments. By default, a sub-tab called "View (decorative)" is selected. However, this automatic selection does not trigger the `select` event on that tab. Thus the user will see something like this.
  
  <img width="1975" alt="Screenshot 2024-12-11 at 16 27 26" src="https://github.com/user-attachments/assets/28ee7b8a-78a0-4a3b-ae65-1a7876ae8240">
  
  Yet, if the user selects another sub-tab, e.g., "View (JSON)" and then selects "View (decorative)", the `select` event is triggered and the user gets to see something like the following.
  
  <img width="1975" alt="Screenshot 2024-12-11 at 16 27 40" src="https://github.com/user-attachments/assets/f73fca00-fb11-452a-8334-f85c127110fa">
  