[WC-3280] DG: Fix unwanted scrollbar for cleared grids

[yordan-st]

Pull request type

Bug fix (non-breaking change which fixes an issue)

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Description

• Clearing a grid to 0 rows, would cause a unwanted recalculation of column widths, causing columns to overflow and in turn add scrollbars. This fix is aimed at making sure that: for empty grids the grid columns use the natural css grid layout instead of recalculating the column widths.
• Setting the datagrid design property to striped would follow an incorrect order of 'striping' each odd row, starting with the second instead of the first row. This was caused by DOM changes introduced in previous DW versions. This is addressed with improved scss selectors.

What should be covered while testing?

• Add a tooltip with a small image in the header filter
• Set the width of that column to auto-fit content and for min-width property try both auto and set by content
• Observe if the column width change weirdly when adding / deleting a row.
• Observe the same if you add / delete and then leave and return to the page.