getAppPickerAdapter
Returns an AbsAdapter instance to be used for the given viewType type.
This method is responsible for providing the appropriate adapter (e.g., for list or grid view) based on the viewType parameter. Subclasses must implement this method to return a concrete adapter that can display the application items in the desired layout.
The returned adapter will be wrapped by a HeaderFooterAdapter to support headers and footers.
Return
The AbsAdapter to use for the specified view type.