MQE-1600: MFTF Vault integration

- prefer credentials from local file over vault
- address review comments

Author: jilu1

src/Magento/FunctionalTestingFramework/DataGenerator/Handlers/CredentialStore.php

@@ -108,8 +108,8 @@ public function getSecret($key)
         }
 
         throw new TestFrameworkException(
-            "{$key} not defined in vault or .credentials file, "
-            . "please provide a value in order to use this secret in a test.\"."
+            "\"{$key}\" not defined in vault or .credentials file, "
+            . "please provide a value in order to use this secret in a test."
         );
     }
 
@@ -140,7 +140,7 @@ public function decryptAllSecretsInString($string)
         // Loop through storage to decrypt all occurrences from input string
         foreach (self::$credStoragePrecedence as $credType) {
             if (null !== $this->credStorage[$credType]) {
-                return $this->credStorage[$credType]->getAllDecryptedValues($string);
+                return $this->credStorage[$credType]->getAllDecryptedValuesInString($string);
             }
         }
     }

src/Magento/FunctionalTestingFramework/DataGenerator/Handlers/SecretStorage/BaseStorage.php

@@ -73,7 +73,7 @@ public function getDecryptedValue($value)
      * @param string $string
      * @return mixed
      */
-    public function getAllDecryptedValues($string)
+    public function getAllDecryptedValuesInString($string)
     {
         $newString = $string;
         foreach (self::$cachedSecretData as $key => $secretValue) {