Partially reverts [59479] and [59461], which previously tried to move some functions from `wp-admin/includes/plugin.php` to `wp-includes/functions.php` so they are available early, so that `get_plugin_data()` can be used.
However, other functions from that file are often used by plugins without necessarily checking whether they are available, easily causing fatal errors. Requiring this file directly is a safer approach to avoid such errors.
Props peterwilsoncc, dd32, swissspidy, johnbillion.
Fixes#62244.
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