[EuiDataGrid] Add column highlighting

[kertal]

Is your feature request related to a problem? Please describe.
We are giving Discover a visual refresh, this issue is a nice to have.
Describe the solution you'd like
Similar to row highlighting, it would be nice to visually highlight columns as the user hovers over the column headers. Figma

[JasonStoltz]

Hey @kertal -- I'm wondering out loud about the user value here. What is the intent of highlighting a column? Is this trying to solve a problem that users have? Or is this a best practice you've seen before?

Just trying to understand this a bit better and gauge it's priority. Thanks!

[kertal]

Sure. forwarding this to @andreadelrio @MichaelMarcialis , because it was part of the Discover redesign

[MichaelMarcialis]

Thanks for the ping, @kertal. Good question, @JasonStoltz. IMO, this is 100% a nice-to-have feature and something I would put at the very bottom of the priority list. The reason for including this as part of our original Discover design refresh pitch was to make it easier for user to see/spotlight the column of data that they may be attempting to take action on or reorder (if/when we get around to adding column dragging support for reordering). This is similar to patterns you might see on other platforms like Google Sheets or AirTable.