Make feature styles compatible with declutter

Return a single style object for image and text for point features as concatenating two styles in an array is not compatible with decluttering

src/ol/format/KML.js

@@ -911,9 +911,8 @@ function createNameStyleFunction(foundStyle, name) {
   textStyle.setOffsetY(textOffset[1]);
   textStyle.setTextAlign(textAlign);
 
-  const nameStyle = new Style({
-    text: textStyle
-  });
+  const nameStyle = foundStyle.clone();
+  nameStyle.setText(textStyle);
   return nameStyle;
 }
 
@@ -932,12 +931,11 @@ function createFeatureStyleFunction(style, styleUrl, defaultStyle, sharedStyles,
     /**
      * @param {Feature} feature feature.
      * @param {number} resolution Resolution.
-     * @return {Array<Style>} Style.
+     * @return {Array<Style>|Style} Style.
      */
     function(feature, resolution) {
       let drawName = showPointNames;
       /** @type {Style|undefined} */
-      let nameStyle;
       let name = '';
       if (drawName) {
         const geometry = feature.getGeometry();
@@ -953,22 +951,19 @@ function createFeatureStyleFunction(style, styleUrl, defaultStyle, sharedStyles,
 
       if (style) {
         if (drawName) {
-          nameStyle = createNameStyleFunction(style[0], name);
-          return style.concat(nameStyle);
+          return createNameStyleFunction(style[0], name);
         }
         return style;
       }
       if (styleUrl) {
         const foundStyle = findStyle(styleUrl, defaultStyle, sharedStyles);
         if (drawName) {
-          nameStyle = createNameStyleFunction(foundStyle[0], name);
-          return foundStyle.concat(nameStyle);
+          return createNameStyleFunction(foundStyle[0], name);
         }
         return foundStyle;
       }
       if (drawName) {
-        nameStyle = createNameStyleFunction(defaultStyle[0], name);
-        return defaultStyle.concat(nameStyle);
+        return createNameStyleFunction(defaultStyle[0], name);
       }
       return defaultStyle;
     }