build(docs-infra): use puppeteer to get a browser for docs examples tests (#35381)

In #35049, integration and AIO tests were changed to use the browser
provided by `puppeteer` in tests. This commit switches the docs examples
tests to use the same setup.

IMPLEMENTATION NOTE:
The examples are used to create ZIP archives that docs users can
download to experiment with. Since we want the downloaded projects to
resemble an `@angular/cli` generated project, we do not want to affect
the project's Protractor configuration in order to use `puppeteer`.

To achieve this, a second Protractor configuration is created (which is
ignored when creating the ZIP archives) that extends the original one
and passes the approperiate arguments to use the browser provided by
`puppeteer`. This new configuration (`protractor-puppeteer.conf.js`) is
used when running the docs examples tests (on CI or locally during
development).

PR Close #35381

aio/tools/examples/run-example-e2e.js

@@ -262,7 +262,13 @@ function runE2eTestsCLI(appDir, outputFile, bufferOutput, port) {
   const config = loadExampleConfig(appDir);
   const commands = config.e2e || [{
     cmd: 'yarn',
-    args: ['e2e', '--prod', '--no-webdriver-update', `--port=${port || DEFAULT_CLI_EXAMPLE_PORT}`]
+    args: [
+      'e2e',
+      '--prod',
+      '--protractor-config=e2e/protractor-puppeteer.conf.js',
+      '--no-webdriver-update',
+      '--port={PORT}',
+    ],
   }];
   let bufferedOutput = `\n\n============== AIO example output for: ${appDir}\n\n`;