menu: Use defer to avoid race conditions with click listeners

[zanmato]

When using .context_menu on a parent element, the window.on_mouse_event would fire before, for example, the tables on_mouse_down so it'd be like this:

1. First right click = no context menu, right_clicked_row is set
2. Second right click = context menu, but with the row from the first click

Before: (Look at Selected row)

https://github.com/user-attachments/assets/5eb89a00-f1ce-4423-b8d7-3ec61b848b83

After:

https://github.com/user-attachments/assets/10033ca4-4c2c-47b5-ace5-6ba745fcfee5

[zanmato]

I also experimented with a global version in root with render_context_menu_layer and window.open_context_menu_at, which worked, but this change is less intrusive

[huacnlee]

Thank you.