Now that we're passing the mode to the viewholders in their bind
methods, there's no real need to pass them into their constructors. This
also allows us to remove the indirection of having the adapter implement
the SelectionHolder interface and have the mode implement it directly.
Change the DiffUtil callback for bookmarks to use the generated equals()
method instead of only checking the title and url fields. This prevents
the BookmarkNode in our state from getting out of sync with the
BookmarkNode the viewholder is bound to.
Show or hide overflow menu for entire list is triggered when mode is changed
For bookmarks, due to implementation of selection and diffUtil,
additional check is necessary for current item (last selected) that is redrawn
Kainalu Hagiwara