qml/TableView(s): Add contentMargin(s), margins and spacing

This MR updates KeyNavigableTableView by adding extranMargin and contentLeftMargin / contentRightMargin and taking them into account in our different views.

In KeyNavigableTableView we want edge to edge backgrounds in our delegate and header, so we implement our own margins implementation like in ExpandGridView. The default values should be the same than ExpandGridView to respect the grid parti pris.

depends !2863 (merged)