[test] fix flaky test writing temp files

These test create temporary folders using test case titles. It started to fail
recently likely due to newer NodeJS version 21.3.0. There are some changes
around `fs.writeFileSync`.

nodejs/node#49884

Same tests were passing on 21.2.0.

This PR changes the test to use simpler names.

Author: jeremymeng

sdk/identity/identity/test/internal/node/managedIdentityCredential.spec.ts

@@ -769,8 +769,7 @@ describe("ManagedIdentityCredential", function () {
     process.env.IMDS_ENDPOINT = "http://endpoint";
     process.env.IDENTITY_ENDPOINT = "http://endpoint";
 
-    // eslint-disable-next-line @typescript-eslint/no-invalid-this
-    const testTitle = this.test?.title || `test-Date.time()`;
+    const testTitle = "azure-arc";
     const tempDir = mkdtempSync(join(tmpdir(), testTitle));
     const tempFile = join(tempDir, testTitle);
     const key = "challenge key";
@@ -838,8 +837,7 @@ describe("ManagedIdentityCredential", function () {
     process.env.IMDS_ENDPOINT = "http://endpoint";
     process.env.IDENTITY_ENDPOINT = "http://endpoint";
 
-    // eslint-disable-next-line @typescript-eslint/no-invalid-this
-    const testTitle = this.test?.title || `test-Date.time()`;
+    const testTitle = "azure-arc-with-resource-id";
     const tempDir = mkdtempSync(join(tmpdir(), testTitle));
     const tempFile = join(tempDir, testTitle);
     const key = "challenge key";
@@ -910,8 +908,7 @@ describe("ManagedIdentityCredential", function () {
     process.env.IMDS_ENDPOINT = "http://endpoint";
     process.env.IDENTITY_ENDPOINT = "http://endpoint";
 
-    // eslint-disable-next-line @typescript-eslint/no-invalid-this
-    const testTitle = this.test?.title || `test-Date.time()`;
+    const testTitle = "azure-arc-with-client-id";
     const tempDir = mkdtempSync(join(tmpdir(), testTitle));
     const tempFile = join(tempDir, testTitle);
     const key = "challenge key";