Refactor: Improve UI and navigation for component listing screens

This commit enhances the user interface and navigation for the ButtonGroup, ProgressIndicator, and BottomAppBar listing screens.

Key changes:
- Updated `ButtonGroupListingScreen.kt`, `ProgressIndicatorScreen.kt`, and `BottomAppBarListingScreen.kt`:
    - Added a back navigation icon to the `TopAppBar`.
    - Made the screen content vertically scrollable.
    - Added a prominent icon, title, and descriptive text for each component type.
    - Improved styling for titles and descriptions using `MaterialTheme.typography`.
    - Added spacing for better visual separation of elements.
    - Updated descriptions for example list items to be more informative.
- Updated `GroupButtonNavGraph.kt` and `ProgressIndicatorNavGraph.kt`:
    - Simplified navigation logic by directly adding routes to the back stack and using `removeLastOrNull` for back navigation.
- Updated `AppRoutes.kt`:
    - Made `ButtonGroupRoutes` implement `NavKey` for consistency.
- Updated `GridTile.kt`:
    - Adjusted layout to use `Box` with `weight(1f)` for the icon, ensuring it centers properly within the available space.
    - Increased icon size and applied `MaterialTheme.typography.labelMedium` to the title text.