add new component `RHFCountry`

[2qp]

Proposed Key Features

• Virtualized List Rendering: implement a virtualized list using @tanstack/react-virtual.
• Search Functionality: Include CommandInput to filter countries by provided keywords.
• Keyboard Navigation: Support navigating and selecting countries, using refs to manage focus without causing re-renders.
• Country Data Integration: customizable dataset via hook (Bring Your Own DataSet).
• Flag Display: display country flags BYOL (Bring Your Own Library).
• Accessibility (a11y): ensure the component is fully accessible, focus, and virtualized list search input.
• Async Mounting Handling: handle async rendering (e.g., in Popover) using MutationObserver and setTimeout to ensure the virtualizer initializes correctly, addressing issues like parentRef being null.
• Responsive Resizing: Use ResizeObserver to re-measure the virtualizer when the container resizes, ensuring proper rendering in dynamic layouts.
• Optional Grouping: Support grouping countries by region (e.g., continents) with a type: "GROUP" structure.
• TypeScript Support: Provide full TypeScript support.