add testID, helps tests find items in the list (#30138)

Summary:
This change adds a testID to each item in the RNTester list.  This helps Appium find items in the list for automated tests.  The change was added in react-native-windows as part of end-to-end test infrastructure changes.    See https://github.com/microsoft/react-native-windows/pull/5555

We'd like to remove this forked file, upstreaming this change will enable us to do that.

## Changelog

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[General] [Changed] - add testID to items in RNTester test list, helps test automation tools find the items

Pull Request resolved: https://github.com/facebook/react-native/pull/30138

Test Plan: Change is currently running in react-native-windows CI loop.

Reviewed By: cpojer

Differential Revision: D24434352

Pulled By: appden

fbshipit-source-id: 998916d8fe4e4e4cd6ac764baabb9fd5f2e312c7

packages/rn-tester/js/components/RNTesterExampleList.js

@@ -39,6 +39,7 @@ const ExampleCard = ({
   const onAndroid = !platform || platform === 'android';
   return (
     <TouchableHighlight
+      testID={item.module.title}
       onShowUnderlay={onShowUnderlay}
       onHideUnderlay={onHideUnderlay}
       accessibilityLabel={item.module.title + ' ' + item.module.description}