fix: Populate xval/yval from calcdata when array-mode selection uses pointNumber

[camdecoster]

Description

Populate xval/yval from calcdata when array-mode selection uses pointNumber. This happens in some map and geo traces.

Closes #7702.

Changes

• Assign values to xval/yval in array-mode > pointNumber hover branch
• Add test
• Linting/formatting

Testing

• Be on master
• Run the following code snippet in Plotly devtools browser console

  Plotly.newPlot(gd, [{
      type: 'scattermap',
      lon: [-74, -118, -87],
      lat: [40, 34, 41],
      mode: 'markers'
  }], {
      map: { center: { lon: -97, lat: 40 }, zoom: 2 },
      width: 800,
      height: 500
  }).then(() => {
      Plotly.Fx.hover(gd, [{ curveNumber: 0, pointNumber: 0 }], "map");
  });

• Note the error that shows up in the console
• Switch to this branch
• Run the snippet again
• Note that the tooltip shows up in the plot without an error

Notes

• This error occurred because there was a branch of the logic that handles array mode that didn't populate xval/yval
• The call to hoverPoints still passed these undefined variables and caused an error for some map/geo traces
• This fix adds those values, but it's a bit of band-aid with a check on the lonlat key. In the future, we might need to add per-trace accessors to get the proper values and make this check schema knowledge-independent

[KoolADE85]

Works as described 💃