test: fix flaky test-webcrypto-encrypt-decrypt-aes

Use Object.assign() to make shallow copies of the object passed to the
test functions. The test functions are passed to Promise.all() so
execution order is not guaranteed. So using the same object in all of
them is a race condition where one test can have side effects in
another.

Fixes: nodejs#35586

test/parallel/parallel.status

@@ -27,8 +27,6 @@ test-worker-memory: PASS,FLAKY
 test-worker-message-port-transfer-terminate: PASS,FLAKY
 
 [$system==linux]
-# https://github.com/nodejs/node/issues/35586
-test-webcrypto-encrypt-decrypt-aes: PASS,FLAKY
 
 [$system==macos]
 

test/parallel/test-webcrypto-encrypt-decrypt-aes.js

@@ -96,10 +96,12 @@ async function testDecrypt({ keyBuffer, algorithm, result }) {
     const variations = [];
 
     passing.forEach((vector) => {
-      variations.push(testEncrypt(vector));
-      variations.push(testEncryptNoEncrypt(vector));
-      variations.push(testEncryptNoDecrypt(vector));
-      variations.push(testEncryptWrongAlg(vector, 'AES-CTR'));
+      variations.push(testEncrypt(Object.assign({}, vector)));
+      variations.push(testEncryptNoEncrypt(Object.assign({}, vector)));
+      variations.push(testEncryptNoDecrypt(Object.assign({}, vector)));
+      variations.push(
+        testEncryptWrongAlg(Object.assign({}, vector), 'AES-CTR')
+      );
     });
 
     failing.forEach((vector) => {