message: test: make YamlLoadFromStringFail less picky about error msg.
  This failed during Google import, since it depended on protobuf library
  internals. Made it more lenient while preserving semantics.
  Risk level: Low
  Testing: envoy OSS and Google internal.
diff: @@ -299,10 +299,9 @@ TEST(UtilityTest, YamlLoadFromStringFail) {
  "Unable to convert YAML as JSON: /home/configs/config.yaml");
  // Verify loadFromYaml throws error when the input leads to an Array. This error message is
  // arguably more useful than only "Unable to convert YAML as JSON".
  - EXPECT_THROW_WITH_MESSAGE(MessageUtil::loadFromYaml("- node: { id: node1 }", bootstrap),
  + EXPECT_THROW_WITH_REGEX(MessageUtil::loadFromYaml("- node: { id: node1 }", bootstrap),
  EnvoyException,
  - "Unable to parse JSON as proto (INVALID_ARGUMENT:: invalid name : Root "
  - "element must be a message.): [{\"node\":{\"id\":\"node1\"}}]");
  + "Unable to parse JSON as proto.*Root element must be a message.*");
  }
  TEST(DurationUtilTest, OutOfRange) {
  