feat(heatmap): add valueShown in heatmap debug state

[rshen91]

Summary

The heatmap debugState will now include a valueShown parameter to show if the value labels for the cells are shown or not based on the config.

...
  // Heatmap debug state
      heatmap: {
        cells: geoms.heatmapViewModel.cells.map((cell) => ({
          x: cell.x,
          y: cell.y,
          fill: RGBATupleToString(cell.fill.color),
          formatted: cell.formatted,
          value: cell.value,
          valueShown: geoms.config.cell.label.visible && Number.isFinite(geoms.heatmapViewModel.cellFontSize(cell)),
        })),
...

Details

The calculation is lifted from canvas_renderers.ts line 77

Issues

Closes #1436

Checklist

• The proper chart type label has been added (e.g. :xy, :partition)
• The proper feature labels have been added (e.g. :interactions, :axis)
• All related issues have been linked (i.e. closes #123, fixes #123)

[nickofthyme]

LGTM