[BottomNavigationView] Allow adding menu items without onItemsChanged being called

Nobody has claimed this yet.

I want to add menu items to BottomNavigationView in code as their configuration is retrieved from the backend.
And that can be done like this:
```
bottomNavigationItems.forEachIndexed { index, item ->
bottomNavigationView.menu.apply {
add(0, item.menuId, index, item.title).apply {
setIcon(item.icon)
}
}
}
```
But when you do that, MenuBuilder.addInternal calls onItemsChanged requesting a relayout after each item is added with is only needed after the last item has been added.

To handle this, MenuBuilder has stopDispatchingItemsChanged.

But BottomNavigationMenu.addInternal prevents this, as it calls startDispatchingItemsChanged internally.

Start with BottomNavigationView and the BottomNavigationMenu.addInternal path described in the issue, then inspect how MenuBuilder.stopDispatchingItemsChanged and startDispatchingItemsChanged affect MenuBuilder.addInternal. Done means multiple menu items can be added without requesting a relayout after each addition, while the final addition still updates the navigation view.

Written by the indexing model from the issue text.