VersionPolicyValidator should use ComposerInspector instead of ComposerUtility

#3345754: Updater should use ComposerInspector instead of ComposerUtility is almost ready.

#3338789: Random failure: "PHP temp directory (/tmp) does not exist or is not writable to Composer." struck again! Re-testing. Although I can reproduce

Testing Drupal\Tests\automatic_updates\Kernel\StatusCheck\VersionPolicyValidatorTest
.....................F                                            22 / 22 (100%)

Time: 01:15.505, Memory: 6.00 MB

There was 1 failure:

1) Drupal\Tests\automatic_updates\Kernel\StatusCheck\VersionPolicyValidatorTest::testNoCorePackagesInstalled
Failed asserting that exception of type "Drupal\package_manager\Exception\StageException" is thrown.

locally…

That failure was caused by \Drupal\Tests\automatic_updates\Kernel\StatusCheck\VersionPolicyValidatorTest::testNoCorePackagesInstalled()'s reliance on modifying Composer's installed.json manually, which no longer has any effect. Plus by a tiny bug in ::getCorePackageName().

I only got it to green, others did 90% of the work.

I had never heard of drupal/core-dev-pinned before today!

You propose \Drupal\package_manager\InstalledPackage to gain a public readonly bool $isDev property — great — but just yesterday that was being worked on in #3345754: Updater should use ComposerInspector instead of ComposerUtility and was removed in favor of ComposerInspector::getRootPackageInfo() returning a devRequires flag for each installed package.

That is what @phenaproxima settled on and you RTBC'd, @tedbow. I was not involved in that pretty significant shift.

So I think the sensible thing to do next is for you to open that follow-up as you envision it, @tedbow 😊

The follow-up doesn't exist yet — clarifying status.