Allow data tile source loader to return a value or a promise

test/rendering/cases/webgl-data-tile-3-band/main.js

@@ -34,7 +34,7 @@ new Map({
 
           const bandCount = 3;
           const result = data.filter((_, index) => index % 4 < bandCount);
-          return Promise.resolve(result);
+          return result;
         },
         tileSize: size,
       }),

test/rendering/cases/webgl-data-tile-loosely-packed/main.js

@@ -53,7 +53,7 @@ new Map({
             }
           }
 
-          return Promise.resolve(output);
+          return output;
         },
       }),
     }),

test/rendering/cases/webgl-mixed-layers/main.js

@@ -66,7 +66,7 @@ new Map({
             labelCanvasSize,
             labelCanvasSize
           ).data;
-          return Promise.resolve(new Uint8Array(data.buffer));
+          return new Uint8Array(data.buffer);
         },
         transition: 0,
       }),

test/rendering/cases/webgl-multiple-layers/main.js

@@ -64,7 +64,7 @@ new Map({
             labelCanvasSize,
             labelCanvasSize
           ).data;
-          return Promise.resolve(new Uint8Array(data.buffer));
+          return new Uint8Array(data.buffer);
         },
         transition: 0,
       }),