chore(Container): remove obsolete files

[sofisl]

This PR removes obsolete structural files for Container that are no longer generated.

Testing Deletions

I attempted to load the deleted classes to prove they do not exist anymore.

Test Script:

<?php
require 'vendor/autoload.php';
echo "Testing deleted classes for Container...\n";
$success = true;
if (!$success) exit(1);

Output:

Testing deleted classes for Container...

BREAKING_CHANGE_REASON=When the PHP client libraries migrated to the modern gapic-generator-php (microgenerator), the generation of automated smoke tests was dropped. OwlBot failed to delete this legacy generated ClusterManagerSmokeTest.php file, leaving it orphaned in the repository for years. Librarian correctly removes it.

For googleapis/librarian#7366