This introduces a few new CSS variables for controlling data table

styles:


--ink-c-data-table-header-hover-text-color: Color used for text when

  hovering over a header.


--ink-c-data-table-row-border-color: Border color when separating

  rows.


--ink-c-data-table-row-border: Border definition when separating

  rows.


On top of this, the background has been changed to pure black (on dark

mode) and white (on light mode), instead of the container color, helping

provide visual separation and better contrast for data.
The alternative row background has changed to be less dark on light

mode.

Made use of this with all the new datagrid work.