within expression returns inconsistent value when point is on the boundary

[zmiao]

When feature is on the polygon boundary, within returns inconsistent value, which will cause flickering styling for the feature.

Reproducable with style:

{
  "version": 8,
  "sources": {
    "points": {
      "type": "geojson",
      "data": {
        "type": "FeatureCollection",
        "features": [
          {
            "type": "Feature",
            "geometry": {
              "type": "Point",
              "coordinates": [ 5, 5]
            }
          }
        ]
      }
    },
    "polygon": {
      "type": "geojson",
      "data": {
        "type": "FeatureCollection",
        "features": [
          {
            "type": "Feature",
            "properties": {},
            "geometry": {
              "type": "Polygon",
              "coordinates": [
                [
                  [-5, -5],
                  [5, -5],
                  [5, 5],
                  [-5, 5],
                  [-5,-5]
                ]
              ]
            }
          }
        ]
      }
    }
  },
  "layers": [
    {
      "id": "border",
      "type": "fill",
      "source": "polygon",
      "paint": {
        "fill-color": "black",
        "fill-opacity": 0.5
      }
    },
    {
      "id": "points",
      "type": "circle",
      "source": "points",
      "paint": {
        "circle-color": [
          "case",
          [
            "within",
            {
              "type": "Polygon",
              "coordinates": [
                [
                  [-5, -5],
                  [5, -5],
                  [5, 5],
                  [-5, 5],
                  [-5,-5]
                ]
              ]
            }
          ],
          "red",
          "blue"
        ],
      }
    }
  ]
}

[1ec5]

mapbox/mapbox-gl-js#9411 tracks the same issue on the GL JS side.