Update usage of abandoned package

[aaemnnosttv]

Feature Description

The true/punycode package is no longer maintained and should be replaced.

Its repository suggests using symfony/polyfill-intl-idn as the recommended maintained replacement which is already installed as a dependency of guzzlehttp/guzzle. We should update our usage of the old package to use the proper PHP internals where safely polyfilled by the Symfony package.

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Acceptance criteria

• The true/punycode package should be removed as a dependency
  • Its use internally should be replaced by core PHP functions idn_to_ascii and idn_to_utf8
• The symfony/polyfill-intl-idn package should be required

Implementation Brief

• Add symfony/polyfill-intl-idn v1.19.0 as a direct PHP dependency (require) in composer.json.
  • The version is important, as later version requires PHP7.
• in includes/Core/Util/URL.php, refactor the class to replace the usage of Google\Site_Kit_Dependencies\TrueBV\Punycode with the native alternatives. which will be safely polyfilled by the aforementioned package.
  • Save the value of Punycode::PREFIX, xn-- as a const field Punycode_PREFIX in the class.
  • Replace the usage of $punycode->decode with idn_to_utf8.
  • Replace the usage of $punycode->decode with idn_to_ascii.
• Remove the true/punycode package from composer.json

Test Coverage

• All tests should continue to pass.

QA Brief

• QA:Eng: Confirm the permute_site_hosts behaviour has not changed.

Changelog entry

• Replace use of the abandoned true/punycode package with symfony/polyfill-intl-idn.

[tofumatt]

IB ✅

[zutigrm]

QA:Eng verified ✅

• idn_to_utf8 and idn_to_ascii are tested in URLTest::test_permute_site_hosts
• Also did smoke test by connecting AdSense module

[aaemnnosttv]

I did a bit of extra testing here just because this has bitten us before when used in an environment without the intl extension just to make sure the polyfill is working as expected.

Confirmed that idn_to_ascii didn't exist from PHP

server:~/example.com$ php -r 'var_dump(function_exists("idn_to_ascii"));'
bool(false)

Confirmed idn_to_ascii was defined by the SK-loaded polyfill 👍

server:~/example.com$ wp shell
wp> $rf = new ReflectionFunction('idn_to_ascii')
=> object(ReflectionFunction)#2939 (1) {
  ["name"]=>
  string(12) "idn_to_ascii"
}
wp> $rf->isUserDefined()
=> bool(true)
wp> $rf->getFileName()
=> string(127) "/.../public/wp-content/plugins/google-site-kit/third-party/symfony/polyfill-intl-idn/bootstrap.php"
wp>