Add default vertical scrollbar to TableView

[AndrewSazonov]

This PR adds the existing EaElements.ScrollBar as the default vertical scrollbar for TableView with AsNeeded policy and interactive behavior enabled.

[seventil]

You can add topInset and topPadding to the ScrollBar if you want to ofset height for the header.
I guess with AsNeeded policy user only sees a narrow indicator-like bar anyway, and they can interact with it if they want, so it's totally OK to define interactive:true.

Here's an example from listview just for reference:

property real _headerHeight: headerItem ? headerItem.height : 0
ScrollBar.vertical: EaElements.ScrollBar {
        policy: listView.scrollBarPolicy
        interactive: listView.scrollBarInteractive
        topInset: listView._headerHeight
        topPadding: listView._headerHeight
    }