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/example-boilerplate.spec.js

@@ -10,7 +10,7 @@ describe('example-boilerplate tool', () => {
     const sharedDir = path.resolve(__dirname, 'shared');
     const sharedNodeModulesDir = path.resolve(sharedDir, 'node_modules');
     const BPFiles = {
-      cli: 19,
+      cli: 20,
       i18n: 2,
       universal: 2,
       systemjs: 7,