Script Loader: Ensure default packages are registered when loaded via load-scripts.php.

Props CantoThemes, ocean90.
Merges [43877] to trunk.
Fixes #45271.
Built from https://develop.svn.wordpress.org/trunk@44237


git-svn-id: https://core.svn.wordpress.org/trunk@44067 1a063a9b-81f0-0310-95a4-ce76da25c4cd