Fix tableheader placement which is broken in the current D8 ToolBar patch

This is related to the offsettopchange event and the offset calculation across different responsive steps.

The position of the toolbar bar and tray are absolute by default, which means they scroll with the page. The table header offset is only needed when the bar and tray are present on the screen.

The position of the toolbar bar and tray is switched from absolute to fixed at the breakpoint 16.5em.

Related to #1827330: Fix overlay placement which is broken in the current D8 ToolBar patch, #1137920: Fix toolbar on small screen sizes and redesign toolbar for desktop.