[js/web] workaround NPM test fetch failure (microsoft#20020)

### Description

Sometimes the `npm test` failed with an error of "TypeError: Failed to
fetch".

I checked the callback entry of the localhost server started by karma.
When the "Failed to fetch" happens, no request is reflected on the
server side. The root cause is still not identified. However, as this
issue only happens sometimes when the browser is just launched by karma
runner, doing retry can workaround this issue for most of the time.

js/web/test/test-runner.ts

@@ -159,7 +159,8 @@ async function initializeSession(
     if (preloadModelData) {
       session = await ort.InferenceSession.create(preloadModelData, sessionConfig);
     } else {
-      session = await ort.InferenceSession.create(modelFilePath, sessionConfig);
+      const modelData = await readFile(modelFilePath);
+      session = await ort.InferenceSession.create(modelData, sessionConfig);
     }
   } catch (e) {
     Logger.error(

js/web/test/test-shared.ts

@@ -15,14 +15,33 @@ export function bufferToBase64(buffer: Uint8Array): string {
   return base64.fromByteArray(buffer);
 }
 
+async function retry<T>(fn: () => Promise<T>, maxRetries = 3, delay = 100): Promise<T> {
+  let retries = maxRetries;
+  do {
+    try {
+      return await fn();
+    } catch (err) {
+      if (retries-- === 0) {
+        throw err;
+      }
+      await new Promise(resolve => setTimeout(resolve, delay));
+    }
+    // eslint-disable-next-line no-constant-condition
+  } while (true);
+}
+
 export async function readFile(file: string) {
   if (typeof process !== 'undefined' && process.versions && process.versions.node) {
     // node
     return fs.readFile(file);
   } else {
     // browser
-    const response = await fetch(file);
-    return new Uint8Array(await response.arrayBuffer());
+    //
+    // use "retry" to workaround the error "TypeError: Failed to fetch" in some test environments
+    return retry(async () => {
+      const response = await fetch(file);
+      return new Uint8Array(await response.arrayBuffer());
+    });
   }
 }