Radial scale point label backdrop color (#8633)

* Radial scale point label backdrop color

* Update default tests

* backdropPadding is a single setting

* Up the tolerance a bit

* Update tick backdrop padding options

test/fixtures/scale.radialLinear/pointLabels/background.js

@@ -0,0 +1,50 @@
+module.exports = {
+  tolerance: 0.01,
+  config: {
+    type: 'radar',
+    data: {
+      labels: [
+        ['VENTE ET', 'COMMERCIALISATION'],
+        ['GESTION', 'FINANCIÈRE'],
+        'NUMÉRIQUE',
+        ['ADMINISTRATION', 'ET OPÉRATION'],
+        ['RESSOURCES', 'HUMAINES'],
+        'INNOVATION'
+      ],
+      datasets: [
+        {
+          backgroundColor: '#E43E51',
+          label: 'Compétences entrepreunariales',
+          data: [3, 2, 2, 1, 3, 1]
+        }
+      ]
+    },
+    options: {
+      plugins: {
+        legend: false,
+        tooltip: false,
+        filler: false
+      },
+      scales: {
+        r: {
+          min: 0,
+          max: 3,
+          pointLabels: {
+            backdropColor: 'blue',
+            backdropPadding: {left: 5, right: 5, top: 2, bottom: 2},
+          },
+          ticks: {
+            display: false,
+            stepSize: 1,
+            maxTicksLimit: 1
+          }
+        }
+      },
+      responsive: true,
+      maintainAspectRatio: false
+    }
+  },
+  options: {
+    spriteText: true
+  }
+};

test/specs/scale.radialLinear.tests.js

@@ -37,12 +37,13 @@ describe('Test the radial linear scale', function() {
         color: Chart.defaults.color,
         showLabelBackdrop: true,
         backdropColor: 'rgba(255,255,255,0.75)',
-        backdropPaddingY: 2,
-        backdropPaddingX: 2,
+        backdropPadding: 2,
         callback: defaultConfig.ticks.callback
       },
 
       pointLabels: {
+        backdropColor: undefined,
+        backdropPadding: 2,
         color: Chart.defaults.color,
         display: true,
         font: {